Build a property calculator — stamp duty, mortgage, rent-vs-buy across 13 countries

const res = await fetch(
  'https://aplicious.com/api/v1/property/stamp-duty' +
  '?country=GB&property_value=450000',
  { headers: { 'X-API-Key': process.env.LAPI_KEY } }
);
const { data } = await res.json();
// { country: "GB", property_value: 450000,
//   stamp_duty: 10000, effective_rate_pct: 2.22,
//   breakdown: [{ band, rate_pct, tax }] }

const res = await fetch(
  'https://aplicious.com/api/v1/property/amortization' +
  '?loan_amount=5000000&annual_rate=8.5&years=20',
  { headers: { 'X-API-Key': process.env.LAPI_KEY } }
);
// { monthly_payment: 43391, total_interest: 5413840,
//   schedule: [{ month, principal, interest, balance }] }

const res = await fetch(
  'https://aplicious.com/api/v1/property/rent-vs-buy' +
  '?property_price=5000000&mortgage_rate=8.5' +
  '&monthly_rent=25000&years=10',
  { headers: { 'X-API-Key': process.env.LAPI_KEY } }
);
// { verdict: "buy", crossover_year: 7,
//   total_cost_buying: ..., total_cost_renting: ... }

const res = await fetch(
  'https://aplicious.com/api/v1/property/rental-yield' +
  '?purchase_price=5000000&monthly_rent=25000',
  { headers: { 'X-API-Key': process.env.LAPI_KEY } }
);
// { gross_yield_pct: 6.0, net_yield_pct: 4.2,
//   annual_rent: 300000, payback_years: 16.7 }

const res = await fetch(
  'https://aplicious.com/api/v1/property/capital-gains-tax' +
  '?country=IN&purchase_price=3000000' +
  '&sale_price=5000000&years_held=3',
  { headers: { 'X-API-Key': process.env.LAPI_KEY } }
);
// { gain: 2000000, tax_type: "LTCG",
//   tax_amount: 200000, effective_rate_pct: 10 }