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Interest-only vs amortizing loan for a renovation with uncertain cash flow
I’m comparing two ways to fund a planned $90,000 renovation scheduled to take about six months: an interest-only mortgage for the initial period or a standard amortizing mortgage from the start.
The interest-only option would preserve more cash during construction, but I’m concerned about the payment reset and the fact that the balance wouldn’t fall during that period. For example, at a hypothetical 7% rate, interest-only payments on $90,000 would be about $525 per month. A 30-year amortizing payment at the same rate would be roughly $599, before taxes and insurance. That’s only about a $74 monthly difference, while the amortizing loan would begin building equity immediately.
The decision gets more complicated if the borrowing is added to an existing mortgage rather than treated as a separate loan. I’d want to compare:
- Payments during the renovation and after the interest-only period ends
- How much cash should remain in reserves after the $90,000 budget is funded
- Whether qualification is based on the lower initial payment or the later fully amortizing payment
- The remaining balance if the property is sold before or shortly after the payment reset
- Whether the home will be occupied long term, or possibly sold once the work is complete
The renovation may improve the property, but I wouldn’t want to assume the full cost comes back in its value. If cash flow is uncertain, does the initial liquidity justify the slower equity growth, or is the standard payment the safer structure even if it leaves less renovation cash available?
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3 replies
The $74 monthly difference is easy to understate because it only compares the initial payments. What would the fully amortizing payment be when the interest-only period ends, especially if the balance is still $90,000 and the rate has reset?
I’d test the post-renovation budget against a higher payment, a construction overrun, and a few months of delayed cash flow. If the project runs 10–15% over budget, would there still be enough reserves after funding the work to handle that payment without relying on the expected increase in property value?
The six-month renovation schedule should be checked against the loan’s actual interest-only terms, rather than assumed to match them. Is the interest-only period fixed, or does it end when funds are fully drawn, construction is certified complete, or a specified number of months has passed?
That timing can create two different risks. A delayed project might leave the borrower paying interest-only longer, with no principal reduction, or the loan could begin amortizing before the renovation produces the expected rental or other cash flow. I’d also confirm whether the payment changes immediately after the period ends and whether any undrawn renovation funds affect the calculation. The budget should work under the post-interest-only payment even if completion and related cash flow are delayed by several months.
The undrawn-funds detail could materially change the six-month cost. Confirm whether interest accrues on the full $90,000 commitment or only on amounts actually drawn. With staged renovation payments, interest-only charges on the drawn balance may start much lower and rise as work progresses. If the lender charges on the full commitment from day one, the roughly $525 monthly estimate applies immediately, even while much of the renovation budget is still sitting unused. I’d also check whether there are draw fees or minimum-interest rules, since those can narrow the apparent cash-flow advantage.