If the house is in joint names and Mrs PA is not earning... then I think you will only need to pay tax on half of any profits, as she can use her tax allowance for her half. OTOH, if you make a loss on the property once mortgage interest, agent's fees and allowable expenses are included, then the downside is you can only offset half that loss against your salaried income. Either way, I think you'll not end up paying much tax.