Absolutely cautiously hope. Remember, he could also be dressing and clean to manipulate a place bck home and lying to you. Idon't want to rain on your parade but my daughter "quit" too...many times and we bought it until she snuck out of the house at night and stole money, etc. Be very cautious. Has he dropped his drug friends? This would be a VERY good sign. That's what my daughter did when she quit. She was very lonely, but not willing to make friends with druggies in the city where she quit. She worked every day, even though she had no car.
Celebrate each day your child shows improvement, but do be leery or you could end up fooled like us. We left my daughter home alone, thinking she was clean, while we went on a two day vacation with our younger kids.She was to walk the dogs and feed them and not have friends in our house and she promised in a very believable way. Our younger kids got bored so we showed up a day early and surprise!!!! Daughter was throwing a big pill party.
So much for being clean.
I just want you to be safe. Also, is he working? Where is the money coming from?
Be happy yet smart and logical. One good day doesn't mean he is better, yet it could so see if it lasts. When he is truly changed, it will be obvious. My daughter was like a new person, yet we still had fears she'd relapse and did not truly believe she was clean for about a year. We were so used to being manipulated and fooled. We had to protect our hearts.
She did quit. It's been a long time now---eleven years.
Hugs and hoping for a new beginning for both of you.