Borrowing Capacity & Constraints
A plain-English look at what really sets your borrowing limit: how much debt you carry against your income, the safety margin banks add to your rate, and how they estimate your living costs.
Why It Matters Now
When rates are high, knowing how banks actually calculate your limit is the difference between an easy yes and a frustrating no — and it's the single thing most buyers misunderstand.
Key Technical Concepts
Debt-to-Income (DTI) Limits
How much total debt a bank will let you carry compared to your income — and why that limit differs from lender to lender.
How Banks Count Your Income
Every bank's calculator treats your income differently — some count more of your bonus, overtime or rent than others.
The 3% Safety Margin
Banks test you as if your rate were about 3% higher than it really is. Here's how that 'safety margin' shrinks how much you can borrow.
How Banks Estimate Your Living Costs
Banks often use a standard estimate of your living costs instead of your real spending — and it can quietly work against you.
Master Lending Frameworks
See how these limits play out in real strategies over at Model Mortgages.