It seems that you don't have a choice but to move there as originally planned?

An option would be to move there and keep looking for apartments, and then move out as soon as you find something suitable.

With regard to buying a house: it seems that you know him well. Does he normally use indirect means to suggest things (such as, suggesting you buy a house when his true purpose is that you don't move in there, or you only stay a year or two)? Or, normally do you find him to be forthright, clear, and direct with you?

Also: does he normally have a kind nature, such that he would genuinely and consistently want you to live there rent-free?

I think that a contract would be a good idea. However, I imagine that if you bring that idea up, he might conclude that you don't trust him. You might then want to say upfront that it is hard to find housing and so for your peace of mind you want to be crystal clear, in writing, about when you must start looking for your next place to live.