Yes, make him pay rent. Get a receipt book and give him receipts and you keep stubs, or better yet, get him to transfer electronically, with name of payment being RENT. That way you can prove he was renting from you, not your defacto who was sharing finances.

I have a close friend who had assets from her divorce. She had her partner who moved in. 2 years later they broke up and she had to share her assets (he didn't have much of his own). He had been cheating and moved in with a new partner who got to share her original assets. Horrible situation.

If you are joining finances then no. If you are splitting costs then of course

Get legal advice & ensure your house, money & other assets are protected. He might not like signing it but don't back down. Protect yourself above all else!

Go see a lawyer. If he wants to move in you need to both be on the same page with bills, groceries, chores etc.

Pre nup, rent yep.