The maximum amount you can borrow with a buy to let mortgage is calculated differently to a normal residential mortgage (ie. where you occupy the property yourself). Although factors such as the type of property you are looking at, your credit history and the amount of deposit you have available are taken into account, your personal income usually isn't. Instead a lender will use the expected monthly rental income to determine the maximum loan available.
However, it should be noted that some lenders now require first time landlords or those with a small portfolio of properties to have a separate, non-related income of at least £25,000 per year as well as the rental income. For more information and advice specific to your circumstances you should contact a mortgage broker and they'll explain everything for you.
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