How to Build a Mobile Home Calculator

const LOAN_TYPES = {
  'fha-title-i-home': { maxAmount: 69678, maxTermYears: 20, minDown: 0.05 },
  'fha-title-i-lot': { maxAmount: 92904, maxTermYears: 25, minDown: 0.05 },
  'fha-title-ii': { maxAmount: null, maxTermYears: 30, minDown: 0.035 },
  'chattel': { maxAmount: null, maxTermYears: 23, minDown: 0.05 },
  'conventional-mh-advantage': { maxAmount: null, maxTermYears: 30, minDown: 0.03 },
  'va': { maxAmount: null, maxTermYears: 30, minDown: 0 }
  };

  function calculateMobileHomeLoan(homePrice, loanType, annualRate, downPaymentPct, termYears) {
  const config = LOAN_TYPES[loanType];
  if (!config) throw new Error('Unknown loan type');

  const downPayment = Math.max(homePrice * (downPaymentPct / 100), homePrice * config.minDown);
  let principal = homePrice - downPayment;

  // Cap at FHA Title I limits
  if (config.maxAmount && principal > config.maxAmount) {
    principal = config.maxAmount;
  }

  const effectiveTerm = Math.min(termYears, config.maxTermYears);
  const monthlyRate = annualRate / 100 / 12;
  const numPayments = effectiveTerm * 12;

  const payment = monthlyRate === 0
    ? principal / numPayments
    : principal * (monthlyRate * Math.pow(1 + monthlyRate, numPayments)) / (Math.pow(1 + monthlyRate, numPayments) - 1);

  const totalPaid = payment * numPayments;

  return {
    monthlyPayment: Math.round(payment * 100) / 100,
    principal: Math.round(principal * 100) / 100,
    downPayment: Math.round(downPayment * 100) / 100,
    totalInterest: Math.round((totalPaid - principal) * 100) / 100,
    totalCost: Math.round((totalPaid + downPayment) * 100) / 100,
    loanType,
    effectiveTerm: effectiveTerm
  };
  }