How referencing checks affordability
Before you sign a tenancy, the landlord or agent will usually run referencing. This covers a credit check, proof of income, previous landlord references and a Right to Rent check in England. The most common affordability test is that your combined gross annual income is at least 30 times the monthly rent (roughly 40% of your income).
If you're sharing, most agents add up all the tenants' incomes, but some check each person can cover their share. If you don't pass, options include a guarantor, paying some rent in advance (where the landlord agrees) or a rent guarantee service.
Budgeting beyond the rent
Remember council tax, energy, water, broadband and contents insurance. A common budgeting rule is to keep rent below about a third of your take-home pay.