Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Buying a building with two flats, can I rent one out and still get a residential mortgage?
It depends on the terms of the mortgage. Generally speaking, residential mortgages specifically prohibit letting out a property without the bank's express permission -- but as you say, that tends to assume that the whole property is being let, not just a part of it. Conversely, buy-to-let mortgages generally prohibit living in the property yourself! The final arbiter as to what is allowed under a mortgage is the mortgage provider; so the safest option is to speak to one or more banks, and see what they say. (Note that if you're changing the use of part of a property from business to residential, you may need to apply for permission; check with your local council.)