SF_COL_Calc.cs

// Version 1: https://pastebin.com/EHkdSBuM
// Version 2: https://pastebin.com/6P8mNPqN
// 		- Fixed display on retirement percentage. (Static number replaced with correct variable)
// 		- Removed annual sales tax for vehicle being included. (Sales tax only applicable when purchasing the vehicle)
// 		- Enforced 401k max yearly contriutions. (IRS-enforces a max annual contribution limit)
// 		- Fixed formatting, and duplicate numbers. (aka, totals being displayed twice)


using System;

class CostCalculator
{
    private const double GrossIncome = 300000;		
	
	// Exemptions
    private const double HealthInsuranceMontly = 815; 		//Based on https://www.coveredca.com/
    private const double RetirementPercent = 12;			// Assuming 8% employer match, and target goal of 20%
	private const double Max401Annual = 23000;				// https://www.fidelity.com/learning-center/smart-money/401k-contribution-limits#:~:text=The%20IRS%20sets%20the%20maximum,2024%2C%20this%20rose%20to%20%2423%2C000.
    
	// Taxes
	private const double StateTaxPercent = 9.875;			// Based on https://maps.cdtfa.ca.gov/ (random street in SF)
    private const double SocialSecurityPercent = 6.2;		// Based on https://www.ssa.gov/oact/cola/cbb.html#:~:text=We%20call%20this%20annual%20limit,for%20employees%20and%20employers%2C%20each.
    private const double MedicarePercent = 1.45;			// Based on https://www.irs.gov/taxtopics/tc751
    private const double AdditionalMedicarePercent = 0.9;	// Also based on https://www.irs.gov/taxtopics/tc751
    
	
	// Renting / Buying Home
	private const double AnnualRent = 14560;				// Based on https://www.apartments.com/rent-market-trends/san-francisco-ca/
    private const double HomePrice = 1200000;				// Based on https://www.zillow.com/home-values/20330/san-francisco-ca/
    private const double PropertyTaxPercent = 1.17;			// Based on https://www.sftaxappeal.com/post/san-francisco-property-tax-calculator#:~:text=For%20the%20fiscal%20year%202023,to%20determine%20your%20tax%20liability.
    private const double MortgageInterestPercent = 7.37;	// Based on https://www.google.com/search?q=current+mortage+rates
    private const int MortgageTermYears = 30;				// Typical term for $$$$
	private const double UtilityMonthlyCost = 240;			// Based on https://californiamoversusa.com/resources/cost-of-living-in-san-francisco-ca/#:~:text=As%20mentioned%20before%2C%20the%20average,example)%20or%20consume%20more%20gas.

	// Transportation
    private const double PublicTransitAnnualCost = 1000;	// Based on Monthly Pass: https://www.sfmta.com/getting-around/muni/fares 
	

	// Car ownership variables... Random numbers for base-model tesla.
	// Fees based on https://www.dmv.ca.gov/portal/vehicle-registration/registration-fees/
    private const double CarPurchasePrice = 40240;			
    private const double CarSalesTaxPercent = 8.6;
    private const double FederalTaxCredit = 7500;
    private const double StateRebate = 2000;
    private const double HomeChargerCost = 2000;
    private const double CarLoanAnnualPercent = 7;
    private const double CarInsurance = 3397;
    private const double CarMaintenance = 538;
    private const double CarTires = 544;
    private const double CarCharging = 1458;
    private const double CarRegistration = 400;

    // Flags
    private const bool Renting = true; // True for renting, false for owning
    private const bool UsingPublicTransit = true; // True for public transit, false for owning a car

    static void Main(string[] args)
    {
        // Set the culture to US English
        System.Globalization.CultureInfo.CurrentCulture = new System.Globalization.CultureInfo("en-US");
        System.Globalization.CultureInfo.CurrentUICulture = new System.Globalization.CultureInfo("en-US");

        // Perform Calculations
        double exemptions = CalculateExemptions(out double healthInsurance, out double retirementContribution);
        double taxableIncome = GrossIncome - exemptions;
        double totalTaxes = CalculateTaxes(taxableIncome, out double federalTax, out double stateTax, out double socialSecurityTax, out double medicareTax, out double additionalMedicareTax);
        double netIncome = GrossIncome - totalTaxes - exemptions;
        double housingCost = CalculateHousingCost(out double propertyTaxes, out double monthlyMortgagePayment, out double annualUtilities);
        double transportationCost = CalculateTransportationCost(out double carLoanAnnualCost);
        double leftOver = netIncome - housingCost - transportationCost;

        // Output Tree-Like Breakdown
        Console.WriteLine($"Gross Income: {GrossIncome:C}");
        Console.WriteLine($"Left Over: {leftOver:C}");
		Console.WriteLine();
		Console.WriteLine();
		Console.WriteLine($"├── Exemptions: {exemptions:C}");
        Console.WriteLine($"│   ├── Health Insurance: {healthInsurance:C}");
		Console.WriteLine($"│   ├── 401k Contribution ({RetirementPercent / 100:P0}): {retirementContribution:C}");
        Console.WriteLine($"│   └── Total Exemptions: {exemptions:C}");
        Console.WriteLine($"├── Taxes: {totalTaxes:C}");
        Console.WriteLine($"│   ├── Federal Income Tax: {federalTax:C}");
        Console.WriteLine($"│   ├── California State Tax: {stateTax:C}");
        Console.WriteLine($"│   ├── Social Security Tax: {socialSecurityTax:C}");
        Console.WriteLine($"│   ├── Medicare Tax: {medicareTax:C}");
        Console.WriteLine($"│   └── Additional Medicare Tax: {additionalMedicareTax:C}");
        Console.WriteLine($"├── Net Income: {netIncome:C}");
        Console.WriteLine($"├── Housing: {housingCost:C}");
        if (Renting)
        {
            Console.WriteLine($"│   └── Annual Rent: {AnnualRent:C}");
        }
        else
        {
            Console.WriteLine($"│   ├── Property Taxes: {propertyTaxes:C}");
            Console.WriteLine($"│   └── Monthly Mortgage Payment: {monthlyMortgagePayment:C}");
        }
		Console.WriteLine($"│   └── Utilities: {annualUtilities:C}");
        Console.WriteLine($"├── Transportation: {transportationCost:C}");
        if (UsingPublicTransit)
        {
            Console.WriteLine($"│   └── Public Transit Annual Cost: {PublicTransitAnnualCost:C}");
        }
        else
        {
            Console.WriteLine($"│   ├── Car Loan Annual Cost: {carLoanAnnualCost:C}");
            Console.WriteLine($"│   ├── Insurance: {CarInsurance:C}");
            Console.WriteLine($"│   ├── Maintenance: {CarMaintenance:C}");
            Console.WriteLine($"│   ├── Tires: {CarTires:C}");
            Console.WriteLine($"│   ├── Charging: {CarCharging:C}");
            Console.WriteLine($"│   └── Registration: {CarRegistration:C}");
        }
    }

    static double CalculateExemptions(out double healthInsurance, out double retirementContribution)
    {
        healthInsurance = HealthInsuranceMontly * 12;
    	double calculatedRetirementContribution = GrossIncome * (RetirementPercent / 100);

    	// Use the lesser of calculated contribution or max allowed
    	retirementContribution = Math.Min(calculatedRetirementContribution, Max401Annual);
        return healthInsurance + retirementContribution;
    }

    static double CalculateTaxes(double taxableIncome, out double federalTax, out double stateTax, out double socialSecurityTax, out double medicareTax, out double additionalMedicareTax)
    {
        // Federal Tax Brackets for Single Filers in 2024
        (double rate, double threshold)[] federalBrackets = new (double, double)[]
        {
            (0.10, 11600),
            (0.12, 47150),
            (0.22, 100525),
            (0.24, 191950),
            (0.32, 243725),
            (0.35, 609350),
            (0.37, double.MaxValue)
        };

        federalTax = CalculateProgressiveTax(taxableIncome, federalBrackets);
        stateTax = taxableIncome * (StateTaxPercent / 100);
        socialSecurityTax = Math.Min(160000, GrossIncome) * (SocialSecurityPercent / 100);
        medicareTax = GrossIncome * (MedicarePercent / 100);
        additionalMedicareTax = GrossIncome > 200000 ? (GrossIncome - 200000) * (AdditionalMedicarePercent / 100) : 0;

        return federalTax + stateTax + socialSecurityTax + medicareTax + additionalMedicareTax;
    }

    static double CalculateHousingCost(out double propertyTaxes, out double monthlyMortgagePayment, out double annualUtilities)
    {
        annualUtilities = UtilityMonthlyCost * 12;
        if (Renting)
        {
            propertyTaxes = 0;
            monthlyMortgagePayment = 0;
            return AnnualRent + annualUtilities;
        }

        propertyTaxes = HomePrice * (PropertyTaxPercent / 100);
        monthlyMortgagePayment = CalculateMonthlyMortgage(HomePrice, 20, MortgageInterestPercent, MortgageTermYears);
        return (monthlyMortgagePayment * 12) + propertyTaxes + annualUtilities;
    }

    static double CalculateTransportationCost(out double carLoanAnnualCost)
    {
        if (UsingPublicTransit)
        {
            carLoanAnnualCost = 0;
            return PublicTransitAnnualCost;
        }

        carLoanAnnualCost = CalculateAnnualLoanCost(CarPurchasePrice, 20, CarLoanAnnualPercent, 5);

        return carLoanAnnualCost + CarInsurance + CarMaintenance + CarTires + CarCharging + CarRegistration;
    }

    static double CalculateProgressiveTax(double income, (double rate, double threshold)[] brackets)
    {
        double tax = 0;
        double remainingIncome = income;
        double previousThreshold = 0;

        foreach (var bracket in brackets)
        {
            if (remainingIncome > bracket.threshold - previousThreshold)
            {
                tax += (bracket.threshold - previousThreshold) * bracket.rate;
                remainingIncome -= bracket.threshold - previousThreshold;
                previousThreshold = bracket.threshold;
            }
            else
            {
                tax += remainingIncome * bracket.rate;
                break;
            }
        }
        return tax;
    }

    static double CalculateMonthlyMortgage(double homePrice, double downPaymentPercent, double annualInterestRate, int termYears)
    {
        double loanAmount = homePrice * ((100 - downPaymentPercent) / 100);
        double monthlyInterestRate = annualInterestRate / 100 / 12;
        int numberOfPayments = termYears * 12;
        return (loanAmount * monthlyInterestRate) /
               (1 - Math.Pow(1 + monthlyInterestRate, -numberOfPayments));
    }

    static double CalculateAnnualLoanCost(double purchasePrice, double downPaymentPercent, double annualInterestRate, int termYears)
    {
        double loanAmount = purchasePrice * ((100 - downPaymentPercent) / 100);
        double annualInterestRateDecimal = annualInterestRate / 100;
        return loanAmount * annualInterestRateDecimal;
    }
}