If that was possible, there wouldn't be a landlord out there not living in their rental property between lets and claiming rent a room relief. You are talking about buying a rental property and would have all the costs and issues associated with it. If you do go down this road, why not live in the property and rent out the second room which by the looks of it would still cover the majority of the mortgage. I don't know what age you are but are you really planning on living with your parents for potentially another 10 years in the hope of building something??