Real estate · super (composes 5 primitives)
Home affordability master
Pull income, debt, and rate from your profile. We chain front-end and back-end DTI, the max responsible housing payment, full amortization on a target home price, rent vs buy crossover, and the 30-year true cost including taxes + insurance + maintenance.
No profile data yet. Fill your profile to skip data entry on every super calc.
Inputs
Load a preset
Result
Stretch — PITI $2,929 exceeds responsible budget by $362.
Action: Drop home price to $324,776 OR add $10,874 more down payment.
- 1
Max responsible housing payment
$2,567
Min(28% × income, 36% × income − $450 other debt)
- 2
Mortgage P&I (30-yr)
$2,432
$375,000 principal at 6.750%
- 3
PITI (P&I + tax + insurance)
$2,929
+ $372 tax + $125 insurance
- 4
Rent vs buy crossover
29.2 years
After 29.2 yrs, cumulative buy < cumulative rent (assumes 3% rent growth)
- 5
30-year true cost
$1,181,982
+$500,607 interest + $127,500 maintenance (1% / yr)
Assumptions & notes
- Front-end DTI cap of 28% and back-end of 36% are conservative — lenders go higher but house-poor risk grows fast above these.
- Maintenance assumed at 1% of home value per year — historical average across owner surveys.
Continue the housing path
Keep going from Home affordability master
Real-estate decisions compound: affordability changes refi risk, refi terms change investment returns, and investment math changes how much house is actually safe.
Try another scenario
Jump between the buyer, refi, and investor presets without leaving the super-calculator layer.
Affordability scenarios
Refi scenarios
Investor scenarios
Companion tools on mitchreise.com
Keep ShowMath as the formula layer, then jump to Reise Tools for richer dashboards, comparison panels, and adjacent housing workflows.
Multi-scenario comparison
What if — ±20% on one input
| Scenario | Annual gross income | Headline | Δ vs baseline | Magnitude |
|---|---|---|---|---|
| −20% (cautious) | $88,000 | Stretch — PITI $2,929 exceeds responsible budget by $876. | $-513 | |
| Baseline | $110,000 | Stretch — PITI $2,929 exceeds responsible budget by $362. | 0 | |
| +20% (aggressive) | $132,000 | Affordable — PITI $2,929 fits in your $3,080 budget. | +$513 |
Try the input with the highest sensitivity (above). The Δ column shows the dollar swing from a 20% move — that's how much room you have for a counter, raise, or hedge.
Goal seek
Solve for an input value
Pick the input you want to vary and the output you care about. We'll find the input value that gets you to the target. Bisection-based; converges in < 50 iterations.
Monte Carlo simulation
Distribution under input uncertainty (500 trials)
We perturb every numeric input with normal-distributed noise (10–25% sigma depending on input type) and run 500 compute trials. The output is a probability distribution, not a single number — closer to how finance actually works.
Most-leveraged inputs (sensitivity analysis)
Where to focus — what moves the answer most
Each input perturbed ±10%; measured impact on Max responsible housing payment. Higher elasticity = bigger lever.
- 1
Annual gross income
Elasticity ↑ 1.00× — 10% change in this input increases Max responsible housing payment by 10.0%.
- 2
Non-mortgage monthly debt payments
Elasticity ↕ 0.00× — 10% change in this input affects Max responsible housing payment by 0.0%.
- 3
Down payment available
Elasticity ↕ 0.00× — 10% change in this input affects Max responsible housing payment by 0.0%.
- 4
Mortgage rate (%)
Elasticity ↕ 0.00× — 10% change in this input affects Max responsible housing payment by 0.0%.
ShowMath is the only calc site that surfaces this. Adjust the highest-leverage input first — that's where small moves create big results.
Chain payload (for the 3D constellation)
{
"slug": "home-affordability-master",
"depth": 1,
"primitives": [
"dti-calculator",
"mortgage-calculator",
"rent-vs-buy-calculator",
"amortization-schedule",
"property-tax-calculator"
],
"composes": [],
"chain": [
{
"key": "dti",
"label": "Max responsible housing payment",
"primitive": "dti-calculator",
"numeric": 2566.6666666666665
},
{
"key": "mortgage_pi",
"label": "Mortgage P&I (30-yr)",
"primitive": "mortgage-calculator",
"numeric": 2432.242862130809
},
{
"key": "piti",
"label": "PITI (P&I + tax + insurance)",
"primitive": "property-tax-calculator",
"numeric": 2929.117862130809
},
{
"key": "rent_vs_buy",
"label": "Rent vs buy crossover",
"primitive": "rent-vs-buy-calculator",
"numeric": 29.166666666666668
},
{
"key": "total_30yr",
"label": "30-year true cost",
"numeric": 1181982.4303670912
}
]
}The chain explained
Each step above corresponds to a primitive calculator. Click any to see the stand-alone version with its own explainer + sources.
- dti calculatorshipping soon
- mortgage calculatorshipping soon
- rent vs buy calculatorshipping soon
- amortization scheduleshipping soon
- property tax calculatorshipping soon
Chains naturally with
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Wealth trajectory
Net worth → savings rate → portfolio growth → retirement projection → Coast FIRE age.
Real estate
Real estate investment chain
Cap rate → cash-on-cash return → mortgage payment → after-tax cash flow → 5-year projection.
Comprehensive plans
Complete financial health (super-super)
Runs Freelancer Tax Master + Wealth Trajectory + Home Affordability Master in sequence and surfaces the top 3 actions.
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