I don't understand that either - and there has been no loss, in fact you've never have bought a house for £15K 15 years ago, I hope that you have been putting to one side all the money you have been saving in not paying rent (which would surely amount to more than £1k a year if our rent in the past is anything to go by!) - so you can then use that as a deposit to get your own place now you are on your own. Your parents obviously need the house, a verbal agreement (IMO) doesn't hold water, it should have been in writing, and presumably would only take effect after they died, not now. I don't understand what's been detrimental to you in all this. You've lived there for 15 years, paying no rent, and to me, the upgrades you've made aren't relevant - you'd have done that wherever you lived. Where have you lost out?