Contract between two ex partners

I ended my partnership with my ex two years ago but he still lives on my property that I own. I need to get a contract between us stating what monetary amounts I’ll be giving him when he moves out as he put money into building the room he lives in on my property. So essentially I’m giving some of his money back to him sense I’m keeping the room on my property. I need assistance doing this so it’s a legally binding agreement. I’d like to find someone to write it up for me. Thanks