The Second Name on Your Loan Buys Years, Not Just Income — and MAS Charges You for Them

We published a piece in July showing that age, not income, is what quietly caps a Singapore home loan: on an identical S$10,000 salary, a 30-year-old can borrow about S$1.15 million and a 50-year-old about S$744,000, because the full-LTV tenure is "65 minus your age." The obvious response is to put a younger name on the loan. It works, and it works better than most people expect — a large part of the gain has nothing to do with the second person's salary. It is also not free, and the price is set by a rule most buyers have never read.

Every household below is an illustrative composite — stated assumptions, computed math, no real client. Figures come from TRIBE's planner engine at the 4% stress rate, a 55% TDSR cap, 75% LTV on a first housing loan, and no other monthly debt obligations.

The number the bank actually uses is not your age

When more than one person borrows, the bank does not use the older borrower's age, or the younger one's, or a plain average. It uses the income-weighted average age (IWAA):

IWAA = (Age₁ × Income₁ + Age₂ × Income₂) ÷ (Income₁ + Income₂)

The tenure then falls out of it: tenure = floor(min(30, 65 − IWAA)) for a loan that keeps the full 75% LTV. That is the exact formula our planner runs, and it is worth being precise about the weighting — it is by recognised income, which is fixed monthly income plus variable income after a 30% haircut, not by headcount. A second name earning nothing moves the IWAA by nothing.

Two consequences follow immediately, and they pull in opposite directions.

The worked case

A is 50, earns S$10,000, no other debts. B is 34, earns S$6,000. Both are Singapore citizens buying their first property together.

The middle row is not a real option — it exists to split the gain. Adding B lifts the loan by S$755,134 in total. Of that, S$446,134 is her income and S$309,000, or 40.9%, is her age. She raises the household's stress-tested budget by 60%, and separately buys six extra years of tenure by dragging the average age down six years.

Now the part that surprises people. B alone, at 34 on S$6,000, could borrow S$691,222. A alone could borrow S$743,557. Two separate loans would total S$1,434,779. Together they can borrow S$1,498,691 — S$63,912 more than the sum of their parts, on identical incomes and identical rules. Nothing was added. The structure blended a young age into an older borrower's tenure, and the annuity maths did the rest.

Tenure is a staircase, not a ramp

Because tenure is floored to whole years, extra income from the younger borrower buys nothing at all until it moves the IWAA past the next integer:

Going from S$6,000 to S$7,000 raises the household's TDSR budget, so the loan still grows — but not one day of tenure comes with it. Between steps, the second borrower's raise is worth only its own income effect.

Her birth year, by contrast, is worth a great deal:

Fifteen years of age difference in the second borrower, with income unchanged, is S$296,903 of borrowing power.

It runs the other way too

The same formula that rewards a young co-borrower punishes an old one — but not always enough to matter. Take a couple aged 32 and 30, each on S$5,000, buying their first home. Their IWAA is 31.0, they get the full 30-year tenure, and they can borrow S$1,152,037.

Bring in a 60-year-old parent earning S$4,000. The IWAA jumps to 39.29 and the tenure falls from 30 years to 25 — a real loss. But the TDSR budget rises from S$5,500 to S$7,700, and the loan rises to S$1,458,784. The parent adds S$306,747 despite costing five years of tenure.

The striking figure is what that parent could do alone. At 60, his tenure is five years, and his S$4,000 supports a loan of S$119,458. Attached to his children's application, the same income is worth 2.6 times that. Whether he should is a different question — he is now an owner and a debtor at 60, which is a decision about his retirement, not about his children's affordability. We wrote about what happens to CPF at 55 and how age caps a loan on its own.

What MAS charges you for the tenure

Here is where the strategy stops being free. MAS's borrower-mortgagor requirement is one sentence long and it closes the obvious loophole:

"A borrower named on a residential property loan must also be the mortgagor of that property."

Banks verify it directly — the borrower has to appear as a purchaser on the Option to Purchase and as a mortgagor on the Land Titles Act mortgage. There is no version of this where B lends her age to the loan and stays off the title.

The guarantor route is closed for the same reason. MAS's companion rule states that if a borrower cannot meet TDSR alone and someone is brought in to help service the loan, "this person will be considered a co-borrower rather than a guarantor, and lower LTV limits will apply to their future housing loan applications." You cannot buy tenure with a signature that carries no ownership.

So the tenure has a price list, and it is worth reading before the OTP is signed:

• ABSD on the highest profile. Joint buyers are assessed on the highest ABSD profile among them. If B already owns a property, the 20% second-property rate applies to the entire purchase — S$399,651 on the S$1,998,255 above, not 20% of her share. That single line can exceed the whole S$755,134 gain in usefulness terms, because it is cash, now, and the gain is only borrowing capacity.
• B's own next purchase gets harder. Her second housing loan drops to a 45% LTV, and her share of this mortgage counts against her TDSR forever after.
• Undoing it costs money. Taking a name off later is a transfer, which means BSD on the transferred share and possibly SSD if you are inside the four-year window. We have worked that through in the decoupling case that does not work and buying under one name versus decoupling.

What the household should actually check

Three tests, in order.

Is the binding constraint tenure or cash? The S$1,498,691 loan on a S$1,998,255 purchase needs S$499,564 of downpayment plus roughly S$69,513 of BSD. A joint application that clears TDSR and then fails on cash has bought nothing — the same failure mode we documented in qualified on paper, failed the cash test.

What does the loan actually cost each month? The S$8,800 is a stress-test ceiling, not an instalment. At a market rate near 1.40%, that 21-year loan costs about S$6,868 a month; at 2.50% it is S$7,650. The 4% floor is deliberate headroom, and treating it as a budget is how households end up genuinely stretched.

Does the second name have a property future of its own? This is the test people skip. If B is a first-timer who intends to buy in her own name later, the tenure she lends today is charged against that plan at 20% of a future purchase price. If she has no such plan, the cost is close to zero and the S$755,134 is close to free.

The mechanism is neutral. It is the second name's own balance sheet, not the arithmetic, that decides whether using it is sensible.

Methodology published. No spin.