I've been asked, and my response is that I have to be honest. If I've known someone ten years but have only seen them sober and responsible for three weeks, that's all the positive observation I can offer. What gets me (and this has happened a few times) is when prospective employers call asking for a reference because someone put my name or my husband's on a job application--without asking or alerting us. I guess they do it because, between our community activism and my husband's profession, our name is familiar with a lot of people. I don't lie. I don't offer damaging information, but I have said, "I have no basis to judge work ethic" -- because if someone is suiting up and showing up, it's not for me to judge if it's a serious effort or a veneer.
Be honest with this guy about what you're willing--and not willing--to do for him. That's my suggestion.
Peace & Love,
Sugah