Ask him if you were living in his house would he want you to pay half the rent. If he says no start packing boxes. He will either reconsider not paying any rent or you may get the better end of this bargan. Think of the money you would save if you put the amount you are paying for rent now into an account. Lazy son or no lazy son that could add up to quite a chunk of money and may be worth it.

Communication. Tell him how you feel about the rent in this house. Do not bring up the other house unless he brings it up first. If he brings that in as an excuse for not paying you, then you can mention that it's directly effecting you and you think he should address the problem with his son. Then you can ask if he moved in with you because he loved you or for other reasons...

Did you know all this when you moved him in? Or did he "suprise" you with the good-for-nothing son ordeal?

I'd get my stuff together first. Make a clear account of all the bills, mortgage or rent, rates etc. Ask him if he can make time for a discussion, don't drop it on him with no notice. It's a difficult situation because you knew he had a son and quite possibly knew what kind of person he was. I'm sad for you that the son is such a layabout, I guess he'd count as baggage in terms of your relationship. I'd talk to my partner and explain that you're feeling a little bit confused by the financial situation. You both work and you both enjoy the home. If your partner has a seperate set of circumstances which he choses not to share with you, eg holding another house elsewhere (for whatever purposes) then that is between him and his bank manager and has nothing to do with the shared responsibility of living together and related costs. If you are a couple that share everything then you may have to share the burden together but it should still be communicated about. Suggest that he (or both of you) talk to the son, expressing concern that he is not contributing to the situation in a positive way and giving him a realistic time frame to find a job an start contributing to his father's outgoings. If he or the son are not willing then that is between them, unless you and your partner consider you to be the son's step-mother, in which case it should be resolved as if you were his mother. Would you kick your own son out? Would you suggest your son moves back in with you so the house can be sold? Would you suggest the son takes a lodger in? I suppose it comes down to whether you consider his son to be your stepson or not. I'd decide that and take it from there.