Start by checking your income, regular spending, credit history and deposit, while allowing for costs such as surveys, valuation fees, legal work and Stamp Duty where applicable. An agreement in principle can indicate how much you might be able to borrow, but it is not a mortgage offer and the lender will make its own affordability and property checks. Compare deals carefully, including the interest rate, fees and early-repayment charges, and consider using an FCA-authorised mortgage adviser if you want help. Check GOV.UK for current first-time buyer support and tax rules, as eligibility depends on your circumstances.