Ritesh Sabharwal CFP®

W.M.W #53: Decode the Home Affordability Formula (3 / 20 / 30 / 40)

Reading time: 5 minutes - June 20, 2026

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Hey Reader

Reserve Bank of India data shows housing dominates borrowing in India like no other category.
Half of India's loans go to one thing: Homes.
Home loans: 49%, Everything else combined: 51%.

And yet, most Indians are clueless to determine if they can truly afford what they're buying.

They walk into a bank. Get told they're "eligible" for X amount of loan. Once they finalize the house and take home loan, then spend the next 20-30 years wondering where their salary goes every month.

The result? EMIs that consume 40-50%+ of income. Stopped SIPs. Delayed personal goals. Zero emergency fund. And one job loss away from financial crisis.

The problem isn't that Indians buy homes. It's that they don't have an idea or framework to check home affordability.

There's a simple framework consisting of four numbers - 3 / 20 / 30 / 40 which is a popular real estate budgeting guideline used by financial planners to determine home affordability.

What is the 3/20/30/40 Rule?

A framework that tells you if a home purchase is truly affordable before you commit to decades of debt.

All four rules must be satisfied together. Meeting just two or three doesn't protect you.

Breaking Down Each Rule

Rule 1: The 3× Income Rule - Home price should not exceed 3 times your annual gross income.

Why 3×? It keeps total debt at a level your income can realistically service even if income drops temporarily.
​The most common violation: Buying a home worth 5-6× annual income.

Bank eligibility ≠ affordability.

Rule 2: The 20-Year Tenure Rule - Home loan tenure should be 20 years or less. Why does tenure matter so much?

₹50 lakh loan at 8.5%:

30-year loan vs 20-year loan:

• EMI difference: ₹4,945/month (saves ₹5K/month)
• Extra interest paid: ₹34.26 lakhs

You save ₹5,000/month on EMI but pay ₹34 lakhs extra over the loan life. The math never favors longer tenure.

Rule 3: The 30% EMI Rule - Monthly home loan EMI should not exceed 30% of monthly gross income.

Why 30%? Leaves enough for:

• Monthly expenses (30-35%)
• Investments and savings (20-25%)
• Emergency buffer (10-15%)

When EMI crosses 40% of income: Investments stop. Emergency fund depletes. One income shock = financial crisis.
​When EMI crosses 50% of income: The home owns you. You don't own the home.

Rule 4: The 40% Down Payment Rule - Try to Pay at least 40% of property value upfront.

₹60 lakh property - 20% vs 40% down payment:

40% vs 20% down payment:

• EMI lower by: ₹10,414/month
• Interest saved: ₹12.99 lakhs

₹12 lakhs more upfront saves ₹13 lakhs in interest and ₹10,000/month in EMI. That's the power of a larger down payment.

The Rule Applied: Step-by-Step

In Hand Annual income: ₹12 lakhs (₹1 lakh/month take-home)

Step 1 - Rule of 3: Max home budget = ₹12L × 3 = ₹36 lakhs
Step 2 - Rule of 40: Down payment = 40% of ₹36L = ₹14.4 lakhs Loan amount = ₹36L - ₹14.4L = ₹21.6 lakhs
Step 3 - Rule of 20: Tenure = 20 years at 8.5% EMI = ₹18,745/month
Step 4 - Rule of 30: 30% of ₹1 lakh income = ₹30,000 (limit) Actual EMI = ₹18,745 = 18.7% of income ✅

All 4 rules satisfied. Home purchased without financial stress.

What finances look like after buying:

Own a home AND build wealth simultaneously. That's the goal.

The Honest Problem: Mumbai, Bangalore, Delhi

The real-world pushback: "How can anyone follow 40% down payment in Mumbai where a 2BHK costs ₹2 crores?"

Fair point. In Tier-1 cities, the rule is difficult to follow perfectly. But it still guides smarter decisions:

If you can't follow Rule 1 (3× income):

• Buy in a suburb or Tier-2 city
• Wait 2-3 years, save aggressively, increase income

If you can't follow Rule 4 (40% down payment):

• Minimum 20% down payment (never below this)
• Each extra 5% saves lakhs in interest
• Don't drain emergency fund for down payment

If you can't follow Rule 2 (20-year tenure):

• Take 25-year loan but prepay aggressively
• Each ₹1 lakh prepayment in Year 1 saves ₹3-4 lakhs in interest
• Target closing in 20 years even if loan is for 25

If you can't follow Rule 3 (30% EMI):

• Absolute maximum: 40% of income
• Beyond 50% = financial stress zone. Avoid at all costs.

👉 Action Steps This Week

☐ Step 1: Calculate your 3/20/30/40 numbers

• Annual income × 3 = Home budget: ₹_______
• Home budget × 40% = Down payment needed: ₹_______
• Down payment saved today: ₹_______
• Gap to fill: ₹_______

☐ Step 2: If gap exists - Set monthly savings target to reach 40% down in 3-5 years.

☐ Step 3: If already house hunting - Run every property through the checklist before visiting.

☐ Step 4: The stress test before signing

• If income drops 30% tomorrow, can I pay this EMI?
• Do I still have 6-month emergency fund after down payment?

If any answer is NO → you're not ready at this price point.

☐ Step 5: If already in a home loan - Check your EMI as % of income. Above 40%? Start aggressive prepayment immediately.

The Bottom Line

The 3/20/30/40 rule can be a guide to fix that with four simple checks:

• 3× income = Maximum home price
• 20 years = Maximum loan tenure
• 30% of income = Maximum EMI
• 40% down payment = Minimum skin in the game

A home bought within these boundaries:
✅ Lets you sleep at night
✅ Allows continued investing
✅ Doesn't make your family pay the price of your ambition

Buy a home you can afford. Not a home that affords the bank a lifetime of interest.

P.S. Forward this to someone who you think can be benefitted from the newsletter. I have created 1 pager to summarize the details for you and your loved ones which you can share ahead as well.

The best home purchase isn't the most expensive one you can technically afford. It's the one that still lets you build wealth after you buy it.

P.S. I write every day to help you make smarter money decisions. Connect with me on LinkedIn👇.

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