How a Sinking Fund Reduces the Financial Burden of Buying a Flat
Purchasing real estate—such as a ৳30,00,000 (30 Lakh BDT) flat—can feel overwhelming when looking only at the total price tag. Most homebuyers take a high-interest mortgage covering 80% to 90% of the property value, which incurs substantial interest payments over a 15- to 20-year horizon.
A sinking fund operates on a proactive principle: you accumulate capital in advance inside an interest-bearing instrument (such as a bank DPS, Mudaraba monthly savings scheme, or treasury bills). By factoring in a realistic 20% to 30% down payment plus ancillary fees, your target is reduced from ৳30 Lakh to a manageable ৳7.5 to ৳9 Lakh.
Target ৳30 Lakh Flat: Down Payment (25% + Fees = ৳9.6 Lakh) vs 100% Cash
| Goal Model | Net Target | 3 Years (8.5% DPS) | 5 Years (8.5% DPS) | Remaining Loan |
|---|---|---|---|---|
| 20% Down Payment + 7% Fees | ৳8,10,000 | ৳19,890 / mo | ৳10,870 / mo | ৳24,00,000 |
| 25% Down Payment + 7% Fees | ৳9,60,000 | ৳23,570 / mo | ৳12,880 / mo | ৳22,50,000 |
| 100% Outright Cash Buy | ৳30,00,000 | ৳73,670 / mo | ৳40,260 / mo | ৳0 (Debt-Free) |
The Sinking Fund Compounding Formula
To calculate the precise monthly contribution (PMT) required to reach a future capital sum (FV) under an effective monthly interest rate (r) across (n) total months, we use the standard ordinary annuity sinking fund formula:
Where r = Annual Rate / 12 and n = Years × 12. Because interest compounds on the accumulated balance month after month, each subsequent contribution generates higher incremental interest than the last.
Frequently Asked Questions (FAQ)
Why should I include registration and legal fees in the down payment sinking fund?
Banks and non-bank financial institutions (NBFIs) typically do not finance registration fees, stamp duty, mutation costs, or utility connection fees as part of the home loan. These must be paid in cash at the time of deed registration, usually adding 7% to 10% to your upfront cash requirement.
How does an 8.5% DPS compare to saving cash under a mattress?
On a ৳9,60,000 target over 3 years, an 8.5% compounding DPS generates over ৳1,11,000 in interest. That means your bank pays over 11% of your down payment for you, reducing your monthly out-of-pocket savings burden.