Smart Money Rules: 8 Rules to Check Before You Buy

Big purchases and loans can shake a family budget. Many people decide based on a seller’s offer or a friend’s advice. A few simple rules can stop that.

This guide covers eight money rules. They cover buying a bike, car, phone or house. They also cover personal loans, credit cards, investing and retirement.

What are the 8 money rules at a glance?

Decision	Rule to follow	Safe limit
Bike	Adapt the 20/4/10 idea	Good down payment, short loan, low running cost
Car	20/4/10 rule	20% down, 4 years, costs within 10% of income
Phone	Pay from savings	No official rule; avoid stretching with EMI
House	EMI-to-income limit	35–40% of take-home pay (banks allow 40–50%)
Personal loan	Compare before you sign	Rates about 8.75–24% a year
Credit card	Full payment rule	Pay 100% of the bill by the due date
Investing	Diversification	Spread across asset classes
Retirement	Compounding	Start early, stay invested

Deepak Gokul holds the CWM® certification, is NISM-Series-XVII: Retirement Adviser Certified, and is an IRDAI Licensed Insurance Advisor. His firm, Deepak Wealth Framework Pvt Ltd, is AMFI Registered as a Mutual Fund Distributor. Deepak has over 19 years of experience helping families in Chennai and across India plan their money.

Which rule should you follow for a car or a bike?

The 20/4/10 rule is a car-buying guide. It has three parts. Pay at least 20% of the price as down payment. Take a loan for no more than 4 years. Keep all car costs within 10% of your gross monthly income. Car costs mean EMI, petrol, insurance and service.

Worked example: a ₹10 lakh car

The 20% down payment is ₹2 lakh. The loan is ₹8 lakh. At an example rate of 9% for 4 years, the EMI is about ₹19,900. Under the rule, that EMI alone needs a gross income near ₹2 lakh a month. With a ₹1 lakh income, choose a cheaper car or a bigger down payment.

For a bike, use the same idea on a smaller scale. Pay a solid down payment. Choose a short loan. Keep EMI, fuel and service costs low.

How much of your income should a home loan EMI take?

Banks check a number called FOIR. It means Fixed Obligation to Income Ratio. It shows how much of your income goes to fixed payments. Most Indian lenders accept a FOIR of 40–50%. Many planners suggest keeping total EMIs near 35–40% of take-home pay.

So a 30% target is a safe personal goal. It is stricter than most advice. Remember that all your EMIs count, not just the home loan.

For example, take-home pay is ₹80,000. A 35–40% limit is ₹28,000 to ₹32,000 for all EMIs. If you already pay a ₹10,000 car EMI, your home loan EMI should stay near ₹18,000 to ₹22,000.

What should you check before taking a personal loan?

Personal loan rates in India range from about 8.75% to 24% a year. Your credit score, income and job profile decide your rate. Many lenders also group employers into categories. A well-known employer may get a lower rate.

Compare three things before you sign:

• The interest rate, and whether it is on a reducing balance or a flat basis.
• The processing fee and any prepayment charge.
• The total amount you will repay.

Please verify the latest rates on the lender’s official website.

Why should you pay your full credit card bill every month?

If you pay the full bill by the due date, you pay zero interest. If you pay even a little less, interest starts. Many Indian cards charge about 3–3.75% a month. That is roughly 36–48% a year.

For example, an unpaid ₹1,00,000 at 3.5% costs about ₹3,500 in interest for one month. You also lose the interest-free period on new purchases. If you cannot pay in full, converting the balance to an EMI often costs about 13–18% a year. That is much cheaper than revolving the balance.

How does diversification protect your money?

Diversification means spreading your money across different asset classes. Examples are equity, debt and gold. When one falls, another may hold steady. This lowers the risk of a big loss from one choice.

SEBI rules for multi-asset allocation funds show the idea. These funds must invest in at least three asset classes. Each class needs a minimum 10% share. But diversification does not guarantee profit. Mutual Fund investments are subject to market risks.

How does compounding help your retirement savings?

Compounding means you earn returns on your past returns too. Time is the key ingredient. Here is an illustration at an assumed 10% a year return. This is not a promise.

Monthly SIP	Years	You invest	Illustrative value
₹5,000	10	₹6 lakh	about ₹10.2 lakh
₹5,000	20	₹12 lakh	about ₹38 lakh

A Systematic Investment Plan (SIP) means you invest a fixed amount every month. Doubling the time more than triples the result. So start early, even with a small amount.

Frequently asked questions

What is the 20/4/10 rule?

The 20/4/10 rule is a car-buying guide. Pay at least 20% of the price as down payment. Take a loan for no more than 4 years. Keep all car costs within 10% of your gross monthly income. Car costs include EMI, petrol, insurance and service. It is a guideline, not a law, so adjust it to your own budget.

How much of my salary should go to EMIs?

Banks often allow total EMIs of 40% to 50% of income. Many financial planners suggest staying near 35% to 40% of take-home pay. This includes home, car and personal loans together. A lower share leaves room for savings and emergencies. Check your own bank’s rules, because limits differ by lender.

Why is credit card interest so high?

Credit cards are unsecured loans, so banks charge more. Many Indian cards charge about 3% to 3.75% a month on unpaid balances. That is roughly 36% to 48% a year. We found no RBI cap on this rate, so please check your card’s latest terms. Paying the full bill by the due date means zero interest.

What is diversification?

Diversification means spreading your money across different asset classes, such as equity, debt and gold. When one falls, another may hold steady. It lowers risk but does not remove it. It also does not guarantee profit. Mutual Fund investments are subject to market risks, so read all scheme related documents carefully.

Why should I start retirement saving early?

Compounding means you earn returns on your past returns. The longer the money stays invested, the faster it grows. For example, at an assumed 10% a year, ₹5,000 a month grows to about ₹10.2 lakh in 10 years and about ₹38 lakh in 20 years. These are illustrations, not promises.

Where can you read more?

Read our home page at deepakwealth.com. For official investor guidance, visit SEBI Investor, AMFI and RBI.

Mutual Fund investments are subject to market risks, read all scheme related documents carefully. This content is for illustrative and educational purposes only. We deal in Regular Plans. Figures were checked on 18 October 2026. Please verify rates and limits from the latest official source before you decide.