Don’t know how to tell Dad he cannot live with us long term.

On numerous occasions, my Dad has come to “visit” me and my family and ends up staying for an extended period of time. It’s nice to have him but it means either having our daughter sleep in our room or giving up office space. We need the office since both my husband and I work from home. I made the mistake of letting him know recently that when he returns to the US from So America that if he needs a place to stay he can stay with us. I blurted this out before thinking it through. It was the “I should be a good daughter.” He’s my Dad and he doesn’t have a lot of money. Now I’m worried that he will come and stay and it’s ok for the short term, but if long term it puts a strain on our space and family dynamics. Not sure now how to express this to him without hurting his feelings.