suncatcher---I have been in your shoes many, many times--with the "you can stay here but you must have a job and no drinking while living here". It feels so reasonable the first day or two--and, it would be for a normally responsible person who just needs a temporary helping hand. But, in my experience, that plan with someone who has a problem with substances or is overly dependent and immature--that plan has m ore holes than a sieve.
I found that I became a reluctant police person---and, he found the most clever ways to get around the rules. Because of the parent-child relationship, there was increasing tension in the air--and arguments ensued--and, my tears followed. It always disintegrated into He**. And, trust me--you will get all the blame for any failure in the plan.
I hate to type these words--because I hate to rain on your parade. And, I do know how much fun it can be to have them in the house for the beginning. (if only it were a visit under more "normal" circumstances...sigh).
Please keep us posted. I want the very best for both of you. Many of us understand how hard this all is.
dandylion