What Loan Instalment Can You Genuinely Afford?

Two different questions with one answer offered

Rohit has been told what instalment he qualifies for. Somewhere between that number and a smaller one lies the amount he should actually commit to, and nothing in the process he has been through is designed to find it.

A lender is assessing the probability of being repaid over the loan's life. That assessment is competent at what it does and it has no view about whether the payment leaves Rohit able to fund his retirement, replace a car, or absorb six months of one income stopping. Those are not the lender's risk.

Affordability is what remains true after the instalment has been paid, and it has to be computed from the household's own budget rather than read off a ratio.

Why the rules of thumb do not help

There are widely quoted rules about what share of income an instalment may consume. This page does not repeat any of them, and the reason is worth stating rather than leaving as an omission.

They are not sourced here — nothing in this repository establishes where any such threshold comes from or what evidence supports it. And more fundamentally, they cannot be right as stated, because two households with identical incomes can have entirely different capacity. One has no dependants, rents cheaply and has a large reserve; the other supports parents, pays school fees and has nothing set aside. A single percentage applied to both is not a measurement of anything.

A ratio is a screening device, useful for deciding which properties to look at. It is not the affordability calculation.

Start from the surplus that actually exists

The honest method takes an evening and produces a number Rohit can defend.

Take dependable monthly income, and be strict about the word — the amount that arrives even in a poor month. A bonus is not dependable income. Variable pay counts at its floor rather than its average. Where a household has two earners, it is worth knowing what the figure looks like on one.

Then subtract everything that is genuinely committed. Living costs, and the honest version rather than the aspirational one — take last year's bank statements rather than an estimate. Existing loan payments. Insurance premiums. School fees. Any support given to family. And the contributions to goals that cannot be deferred, which means retirement above all: an instalment funded by stopping retirement contributions is not affordable, it has just moved the cost somewhere invisible.

What remains is the true surplus, and it is usually a good deal smaller than the number people carry in their heads.

The instalment is not the housing cost

The most consequential error at this point is comparing the proposed instalment against current rent and concluding the difference is manageable.

Ownership brings costs that rent does not: maintenance or society charges every month, property tax every year, insurance, and repairs — irregular, forgotten between occurrences, and occasionally large. A new location may change commuting costs. Moving in brings furnishing.

So the instalment has to be compared against the surplus after all of those have also been subtracted. A couple who can meet the instalment but not the instalment plus the ownership costs have discovered the problem in month four rather than in the spreadsheet.

Then take a margin, deliberately

Committing the entire remaining surplus to the instalment produces a household with no capacity for anything, and the things it has no capacity for are certain to happen.

The margin should be large enough to absorb the ordinary bad year rather than the catastrophe. The test worth running is specific: if one income stopped for some months, or a large repair arrived, or the rate on a floating loan moved up, would the payment still be made without borrowing, without raiding the emergency reserve, and without stopping the retirement contribution?

That last clause is the one that gets quietly dropped. A household that copes by suspending its investing has not coped; it has paid for the instalment with a goal it will not notice missing for twenty years.

The rate point deserves its own line for a floating-rate loan. The affordability test is worth running at a rate meaningfully above the one offered, because the instalment being agreed to is not fixed for the loan's life. The common practice of holding the instalment steady and extending the term instead makes a rise easy to miss — which is why the balance and the remaining payments are the numbers to check after every reset, not the instalment.

What a smaller instalment actually buys

It is worth naming the benefit, because the cost — a smaller or differently located flat — is vivid and the benefit is abstract.

A comfortable margin means a job change is possible. It means one earner can take a break. It means a bad year is an inconvenience. It means the retirement contributions continue through all of it, so the twenty-year plan survives the five-year turbulence. And it means the loan stops being the thing that determines every other decision the household makes for the next two decades.

None of that appears in the sanction letter, and all of it is what the margin is for.

The check to run before signing

Three questions, and the loan is affordable when all three are yes.

Does the instalment plus every ownership cost fit inside the true surplus, with a margin left over? Does it still fit if one income stops for a few months, or if the rate rises? And do the non-negotiable goals — retirement, insurance, the emergency reserve — continue untouched in both the normal and the stressed case?

If the answer to any of those is no, the instalment is too large. The available responses are a smaller loan, a larger down payment, a longer term — noting that the last stretch of term is the most expensive — or waiting, which is a position rather than a failure.

What to take away

The lender's number measures the lender's risk. Yours is what remains true afterwards, and it cannot be read off a percentage of income because two households with the same income can have completely different capacity.

Build it from dependable income minus honest living costs, existing commitments and the goal contributions that cannot be deferred. Compare against the instalment plus every cost of ownership, not the instalment alone. Then keep a real margin, and test it against one income stopping and against a higher rate — with the retirement contribution untouched in both cases. If it only works in the good case, it is not affordable yet.