Suggest you check, or have checked for you, the small print of Terms and Conditions associated with exercising your right to buy. Terms do vary but if was a council I'd not allow this for a minimum number of years since it defeats the objective of selling the houses to tenants. Buy to Let mortgages are generally for investors who have an existing mortgage on their existing dwelling - and can't remortgage the existing dwelling enough to rise the capital to invest in another house. If you are saying you are in another house anyway (with a mortgage), surely that exempts you from a right to buy anyway, since you aren't living in the house?