The client
A purchase in Peterborough, Ontario at $395,000 includes a legal secondary suite occupied rent-free by an aging parent — family support, not a tenancy, and no money changes hands for it at all.
Purchase price
$395,000, 10% down
Peterborough
Secondary suite
Legal, occupied by a parent
$0 rent collected -- family support, not a tenancy
Buyers' own income
$8,900/month
Both salaried, combined
Other debt
$310/mo car loan
Unchanged throughout
What the buyers had assumed
The suite would help them qualify
It contributed exactly zero to either ratio
The problem
Every rental or secondary-suite file the buyers had heard about treated a portion of the rent as income toward qualifying — an add-back or offset, sized to whatever the tenant actually pays. This suite has a tenant of a kind — a parent living there — but no rent, at all, is being collected. Not a discounted family rate, not an under-market figure the lender might haircut. Zero.
Real rent vs. no rent
- ▸Every other rental file in this category involves REAL rent, at some level, being partially counted
- ▸This suite generates $0 in actual payments -- the market rent it could command, $1,400/mo, is purely hypothetical
- ▸A lender counts income that is actually being collected, not income a unit is theoretically capable of producing
The buyers weren't wrong that secondary suites often help a file qualify. They were wrong about which suites do — and the correction here was not a negotiation with the lender, it was simply pricing the file to the fact that no money was actually changing hands.
The numbers
The contrast is the whole point: what the file would have looked like under a mistaken assumption, against what it actually is.
| The insured purchase, with zero rental contribution | Amount |
|---|---|
| Purchase price | $395,000 |
| Down payment (10%) | $39,500 |
| Base mortgage | $355,500 |
| CMHC premium — 3.10% in the 85.01-90% LTV band | +$11,020 |
| Total insured mortgage | $366,520 |
| TDS, mistaken assumption vs. correct treatment | If a 50% add-back had been assumed | Correct (zero rental income) |
|---|---|---|
| Income used to qualify | $9,600/mo ($8,900 + $700 notional add-back) | $8,900/mo (buyers' own income only) |
| Mortgage payment at the qualifying rate | $2,545 | $2,545 |
| Property tax and heat | $460 | $460 |
| Car loan | $310 | $310 |
| Total debt service | 34.5% | 37.2% |
The correct file still passes comfortably — 37.2% against CMHC's 44% maximum — but it passes because the buyers' own income was always strong enough on its own, not because of anything the suite contributed. TDS moved 2.7 points purely from removing a notional figure that was never real.
The solution
A mortgage agent licensed under Ontario's Mortgage Brokerages, Lenders and Administrators Act corrected the buyers' expectations before the file was even submitted, rather than presenting a number the underwriter would have removed anyway.
First, confirmed directly with the buyers that no rent is, or has ever been, collected on the suite. This wasn't a below-market family rate to document and partially count — it was genuinely zero, which changes the entire treatment.
Second, re-sized the file from the start on the buyers' own $8,900/mo income, with no rental offset of any kind. Presenting the suite as income-producing and having an underwriter correct it mid-file would only have cost time.
Third, documented the suite's occupancy honestly as family support, not a tenancy. This avoided any appearance of misrepresenting an arrangement that was never going to generate qualifying income in the first place.
The outcome
The file funded insured at 4.90%, GDS 33.8% and TDS 37.2%, both comfortably inside CMHC's maximums, with the secondary suite contributing exactly nothing to either ratio — because it was never generating income to contribute.
GDS and TDS maximums (39% / 44%) apply directly because this is an insured purchase; both ratios passed with room to spare on the buyers' own income alone, before any rental consideration at all.
What to take from this file
- 01A rent-free family arrangement is not below-market rent -- it is zero rent. The distinction matters: below-market rent can sometimes be partially counted; zero income cannot be counted at all.
- 02A unit's market-rent potential is not the same as its actual income. A lender qualifies against money that is actually changing hands, not against what a suite could theoretically command.
- 03Confirm the real rent situation before assuming any add-back or offset applies. Every other rental file's treatment depends on real rent being collected at some level -- assuming it applies here would have been a straightforward error.
- 04Size the file to the income that will actually count, from the first conversation. Presenting an inflated qualifying income and having it corrected mid-file only wastes time and risks the buyers' confidence in the numbers.
- 05A family member living rent-free in a secondary suite is a housing decision, not an investment strategy. Treating it as one, for qualifying purposes, misunderstands what the lender is actually being asked to underwrite.
Sources
Every regulatory figure in this file traces to one of these primary sources. Client details and anything that varies by lender are illustrative, as flagged below.
- ▸CMHC — Purchase (Mortgage Loan Insurance) — default-insurance premium schedule by LTV band (25-year amortization).
- ▸CMHC — CMHC Home Start — minimum down payment tiers (5%/10%) and the $1.5M insured price cap.
- ▸OSFI — Minimum qualifying rate for uninsured mortgages — the minimum qualifying rate — greater of contract rate + 2% or 5.25%.
- ▸CMHC — CMHC Reviews Underwriting Criteria — GDS 39% / TDS 44% maximums and the 600 credit-score floor for insured files.
- ▸Provincial/territorial mortgage-broker legislation fetched directly (bclaws.gov.bc.ca, legisquebec.gouv.qc.ca, fcaa.gov.sk.ca, web2.gov.mb.ca, nslegislature.ca, assembly.nl.ca) plus FCNB's own site for NB and CanLII's index for PE — see notes for per-province method — provincial mortgage regulators and licence titles.
Illustrative in this file — lender-specific, not rules:
- ▸4.90% contract rate — rates move daily; not a quote.
- ▸the illustrative 50% add-back scenario — shown only to contrast against the correct treatment -- no rent is actually being collected on this file, so no add-back applies at all.
Authority & provenance
How this case file was built
We publish the origin, the verification method and the reviewer for every case file, so you can judge how far to trust it before you rely on it with a client.
Where it comes from
Derived from files handled by Treadstone’s fulfillment desk and from scenarios contributed by partner brokerages. Names, employers, exact amounts and dates are changed so no client or file is identifiable.
Provenance: Composite — a pattern seen repeatedly on fulfilled files, not a single transaction.
What is verified
Every regulatory figure traces to a primary source listed above and was checked against it on the date shown. The arithmetic is recomputed by machine on every rebuild.
Anything that varies by lender is labelled illustrative rather than stated as a rule.
Who reviewed it
Reviewed for Canadian regulatory accuracy before publication, and re-checked whenever a cited rule changes.
Reviewed by: Nicholas Parson, Treadstone Associates — reviews every case file before publication.
This case file is professional reference material for licensed mortgage professionals. It is not advice to a borrower, and it is not a lender commitment. Insurer rules, qualifying rates and provincial taxes change — confirm the current position with the insurer, regulator or lender before you rely on any figure here in a live file.