Dude, I know that I don't know you, but... You're 20, so you probably have friends and hang out with people (at least I hope). What do you say to everyone who asks "who lives in that room", "why's it always closed"... nevermind the landlord, some dumb shit who is friends with one of your friends friends is going to hear that someone is growing at your house. And that dumb ass will either think it's a good idea to steal everything, or he will be a jealous bitch and call the cops on you.
I'm sure there are many young ones on here (say 22 and under) that grow just fine. I'm not saying it can't be done, but there are too many stupid people your age to trust. I don't mean you or your potential roommate either (you could be dumb, but that's not what i'm saying). It's just too risky in my opinion. If you really trust your roommate then grow in your own closet. Don't tell anyone else but him, and tell him not to tell anyone.
About the 24 hours notice, I think it is legal that they have to, but I've had 3 landlords knock on my door unannounced and if I would have told them to come back in 24 hours they definitely would have thought something was up, even if it is legal.
Good luck no matter what bro.