If you are looking at buying a buy-to-let property at £320,000, with a deposit of £50,000 your mortgage will be £270,000. This makes your loan to value (the percentage of the loan against the value of the property you are borrowing against) 85%. Currently there are very few lenders operating at this level in the buy-to-let market, and the amount you can borrow will be largely based on the potential rental.
Lenders also typically like to see the rent covering the mortgage payments by at least 125% either at the pay rate or a notional rate, usually 5%. As an independent, whole of market mortgage broker we have a huge range of lenders that we work with which means we have more options available to us.
We would need to discuss the details with you, so the best thing to do would be to contact one of our mortgage experts on 020 4519 5101 and talk it through with them.