Short answer：Funding one property from another links their cash-flow risks. Confirm permitted letting and financing uses, then test vacancy, higher rates and repairs occurring together.
Start with collected net cash
Gross contractual rent is not the amount available. Deduct vacancy, owner-paid costs, tax and existing loan payments. Owner-occupied mortgage-insurance terms should not be assumed to permit letting or investment borrowing.
Test linked shortfalls
Combine both properties and household spending in one statement. Assess how long obligations remain manageable if one income source stops. Refinancing and sale take time and are not committed emergency funding.
Before deciding
- Check letting and lending restrictions
- Avoid counting the same rent twice
- Keep reserves independent of property income
Sources and method
Sources support the specific rules described. Checklists and hypothetical calculations are editorial explanations, not measured market results or individual approvals.
Revision：Removed unsupported experience, case outcomes and statistics; corrected the topic-specific rules and limitations described above.
Scope：General information only, not personalised legal, tax, immigration, admissions or investment advice.