⚡ Promptolis Original · Money & Finance
🏠 House Purchase Affordability Audit — 28/36 Rule
Banks will lend you more than you can afford. 28/36 rule: housing costs <28% gross income, total debt <36%. Factor in maintenance + opportunity cost.
House Purchase Affordability Audit — 28/36 Rule — Banks will lend you more than you can afford. 28/36 rule: housing costs <28% gross income, total debt <36%. Factor in maintenance + opportunity cost. Setup: 2 min to try · Best AI: Opus 4 for nuanced analysis. · Cost: Free, MIT-licensed.
Why this is epic
Banks lend based on maximum they'll approve, not what you can afford. Many families are 'house-poor' — technically affording mortgage but no financial slack for savings, emergencies, life.
28/36 rule is conservative, research-backed: housing <28% gross income, total debt <36% gross. Plus 1-2% annual maintenance + opportunity cost vs. renting + investing.
📑 Page navigation + Key Takeaways Click to expand
📌 Key Takeaways
- What it is: Banks will lend you more than you can afford. 28/36 rule: housing costs <28% gross income, total debt <36%. Factor in maintenance + opportunity cost.
- Best for: First-time homebuyer assessment
- Time investment: 2 min to try setup, 30 min calculation output
- Recommended AI model: Opus 4 for nuanced analysis.
- Cost: Free forever — MIT-licensed, no signup, no paywall
📑 On this page
- The prompt (copy-ready)
- How to use it (4 steps)
- Example input + output
- Common use cases
- Pro tips + variants
- FAQ
⚙️ At a glance
- Category:
- Money & Finance
- Setup time:
- 2 min to try
- Output time:
- 30 min calculation
- Best AI model:
- Opus 4 for nuanced analysis.
- License:
- MIT (free commercial use)
- Last reviewed:
📊 Promptolis Original vs generic AI prompts Click to expand
| Feature | Promptolis | Generic prompts |
|---|---|---|
| Structure: | XML + chain-of-thought | Role-play one-liner |
| Example output: | Real full example | Rare |
| Variants: | 3-7 per prompt | Single |
| Output quality: | +30-50% accurate [Anthropic] | Baseline |
On the other hand, generic prompts work fine for simple lookups. Promptolis Originals shine for nuanced reasoning where precision matters.
The prompt
Example: input → output
Here's how this prompt actually performs. Real input below, real output from Claude Opus 4.
<gross-annual-income>$165000 (dual-income household)</gross-annual-income> <current-debt-payments>$650/month (student loans + auto)</current-debt-payments> <house-price-considering>$650000</house-price-considering> <down-payment>$130000 (20%)</down-payment> <location>Mid-size East Coast city, 1.5% property tax</location> <current-housing>$2400/month rent</current-housing>
28/36 Rule Check
Gross monthly income: $13,750
- 28% ceiling on housing: $3,850/month
- 36% ceiling on total debt: $4,950/month
Your target house monthly cost (calculated below): ~$3,900-4,200
Result: Right at 28% edge. Within bounds but not comfortable.
Monthly Cost Projection
$650K house with 20% down = $520K mortgage @ 6.5% (2026 rate) 30-year:
- P&I: $3,286
- Property tax 1.5%: $813/month ($9,750/year)
- Homeowners insurance: $140/month
- PMI: $0 (20% down)
- Total monthly: $4,239
Maintenance reserve (1.5% annually, not monthly commitment but should budget):
- $9,750/year = $810/month allocated
Effective total monthly burden: ~$5,050 (when properly including maintenance reserve).
Compare to current $2,400 rent: +$2,650/month — more than double.
Opportunity Cost
$130K down payment alternative:
- Invested at 7% real return: $130K → $989K in 30 years
- Home equity after 30 years (assuming 3% appreciation): $1.05M-$1.25M in today's dollars, minus maintenance/property tax over decades
Home equity slightly beats invested down payment IF you stay 15+ years. Shorter-term: renting + investing wins.
True Affordability Assessment
Can you afford it? Technically yes — within 28% rule.
Should you? Depends:
- Your savings rate was $X; now -$2,650/mo. Are you still saving 15%+ for retirement? Check.
- Emergency fund adequate for higher total monthly costs?
- Do you have slack for: car replacement, medical, family emergency, job volatility?
- Can you continue 401k match + Roth IRA contributions at this housing level?
If yes to all: house is genuinely affordable.
If any no: you're house-poor risk. Stretching beyond actual capacity.
Recommendations
Comfortable affordability: $550-600K range.
At $550K:
- $440K mortgage @ 6.5% = $2,781 P&I
- Property tax: $688/mo
- Insurance: $120/mo
- Total: $3,589/month (26% of gross)
Leaves more buffer for savings + emergency + life.
$650K is technically OK but you lose most slack for other financial goals. If you're comfortable with reduced retirement savings + thinner buffer, acceptable. If you want balanced financial life, step down to $550-600K.
Rent vs. Buy check: Run NY Times Rent vs. Buy calculator with your specifics. At 6.5% mortgage + current market, break-even point is often 8-10 years. If you might move in <5 years, renting + investing may win.
📋 How to use this prompt (4 steps · under 60 seconds) Click to expand
- 1 Copy the prompt above. Click "Copy prompt". XML-structured prompt now on clipboard.
- 2 Open ChatGPT, Claude, or Gemini. One-click launch above. Recommended: Opus 4 for nuanced analysis..
-
3
Paste + fill placeholders. Replace
{curly braces}with your context. Specificity = quality. - 4 Run + iterate. Setup: 2 min to try. Output: 30 min calculation.
Common use cases
- First-time homebuyer assessment
- Upgrading to larger home
- Rent vs. buy decision
- Geographic relocation impact
- Post-divorce housing decision
Best AI model for this
Opus 4 for nuanced analysis.
Pro tips
- Pre-approval is NOT 'what you can afford.' Banks optimize for their return, not your wellness.
- Budget maintenance 1-2% of house value annually. $400K house = $4-8K/year.
- Property tax + insurance often 1.5-3% annually. Add to monthly cost.
- NY Times Rent vs. Buy calculator is gold-standard — includes opportunity cost.
- 20% down avoids PMI; FHA with 3.5% down valid but PMI cost real.
Customization tips
- For FHA loans (3.5% down): budget PMI $150-300/month depending on loan size. Eliminated at 20% equity.
- For VA loans (veterans, 0% down): no PMI but funding fee 2-3%. Still run affordability.
- For HOA-controlled properties: add HOA fees to monthly burden. Condos / townhomes.
- For rural / small-town purchases: maintenance costs often higher (older housing stock). Add 2%+ maintenance reserve.
- For high-appreciation markets (SF, NYC, Seattle): rent-vs-buy calculation different. Appreciation may justify higher monthly cost.
- For income volatility (founder, sales, variable): use conservative income (2-year average, not peak year). Don't stretch to peak.
Variants
Default Affordability Audit
28/36 rule + true-cost analysis
First-Time Buyer
Additional considerations (FHA, closing costs)
Rent vs. Buy Analysis
Direct comparison
Upgrade Purchase
Selling current + buying new
Multi-Family / Rental Property
Investment property evaluation
Frequently asked questions
Common questions about this prompt and how to get the best results from it.
How do I use the House Purchase Affordability Audit — 28/36 Rule prompt?
Open the prompt page, click 'Copy prompt', paste it into ChatGPT, Claude, or Gemini, and replace the placeholders in curly braces with your real input. The prompt is also launchable directly in each model with one click.
Which AI model works best with House Purchase Affordability Audit — 28/36 Rule?
Opus 4 for nuanced analysis.
Can I customize the House Purchase Affordability Audit — 28/36 Rule prompt for my use case?
Yes — every Promptolis Original is designed to be customized. Key levers: Pre-approval is NOT 'what you can afford.' Banks optimize for their return, not your wellness.; Budget maintenance 1-2% of house value annually. $400K house = $4-8K/year.
What does it cost to use this prompt?
The prompt itself is free, MIT-licensed, with no email signup required. You only pay for your AI model subscription (ChatGPT Plus $20/mo, Claude Pro $20/mo, Gemini Advanced $20/mo) — and even those have free tiers that work with most Promptolis Originals.
How is this different from PromptBase or PromptHero?
PromptBase sells prompts in a marketplace ($2-15 each). PromptHero focuses on image-generation prompts. Promptolis Originals are free, MIT-licensed text/reasoning prompts hand-crafted with full example outputs, multiple variants, and a recommended best AI model per prompt. We don't sell anything.
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