Deposits, costs and what a household can carry

There are two affordability questions and only one of them is asked by a lender. The lender asks what can be borrowed against this income. The household has to ask what can be carried through the next decade.

The deposit is not the only cash needed

A purchase requires the deposit plus a set of one-off costs that arrive at the same moment: legal fees, survey, any transaction taxes that apply, lender fees, removals, and the immediate work that turns a house into a home someone can live in. Households that plan to the deposit alone find themselves borrowing expensively for the rest at exactly the point their reserves are lowest.

Why the deposit affects the rate

Because lending is priced in loan-to-value bands, the deposit does two jobs: it reduces the amount borrowed and it may reduce the price of what is borrowed. Between bands, additional deposit only does the first. This is the practical reason a household close to a band boundary is often better served by waiting a short period than by stretching.

The running costs

Ownership carries costs that renting either avoids or bundles invisibly into the rent. Buildings insurance. Maintenance, which is not optional and does not arrive evenly. Any service charge or ground rent where applicable. Local property taxes or charges. Energy, which varies enormously with the fabric of the building — a point worth taking seriously when comparing two properties at the same price.

Maintenance is the item most often left out. Buildings consume a share of their value every year in roof coverings, heating plant, decoration, windows and drainage. Spending nothing for several years does not remove the cost; it defers it into a larger single bill.

Stress testing at home

The useful private exercise mirrors the lender's. Take the payment, apply a materially higher rate, add the running costs above, and ask whether the resulting figure still leaves the household able to absorb an ordinary shock: a boiler, a car, a period of reduced income. If the answer depends on nothing going wrong, the number is too high regardless of what a lender is prepared to advance.

Reserves

A separate reserve, held in cash and not committed to the purchase, is what converts a bad month into an inconvenience. It is also what stops the first significant repair from being financed on expensive short-term credit. Households often treat the reserve as the flexible part of the plan. Structurally it is the part that makes the rest of the plan safe.

Two common framing errors

The first is comparing a mortgage payment with a rent and concluding ownership is cheaper. The comparison is only meaningful once the running costs above are added to the mortgage side. The second is treating the maximum offered as a target. A lender's maximum is a limit derived from standardised assumptions about a household it has never met; it is a ceiling, not a recommendation.

Nothing here is financial advice, and no figure in this piece is offered as a benchmark. The purpose is only to make the shape of the arithmetic visible.