That's a decent idea. Ever seen How High? (http://www.imdb.com/title/tt0278488/). High quality it is.

Do you have a background in photography/cinematography? I can see a few ways this could end up, a decent movie shot on a $500 miniDV camera and posted on youtube, or a joke that no one thinks is funny, or a decent first run project.

By no means am I trying to be mean, but even with a great script (your plotline has potential) you can end up with a steaming pile of shit. The thing about drugs and comedy is that you usually end up with some hippie-looking fellow who looks captivated by his hands and keeps saying "whoa man".

I highly reccomend you see "Requiem for a Dream", a highly excellent movie about drugs and how they ultimately tear everyone in the movie apart. It's mostly about heroin, and (spoiler warning) it leads to one kid being arrested miles from home, being called a "dopefiend nigger" at his new prison, one kid losing his left arm and then being jailed, arm-lost-kid's girlfriend sucking dick for drugs and then putting on a big lesbian sex show for more drugs, arm-kid's grandma being hospitalized because she was taking speed to loose weight

It's a drama, but the cinematography is amazing as Aronofsky's always is, and might give you some good ideas.

As for getting money to film it, that's always the hard part, but I strongly suggest you offer torrents of it for free, but ask people to donate or buy the dvd with a nice case and poster or whatever for like $25 or something.

Anyways, good luck with that, and if you need some help with anything, I'm sure the collective knowledge of this site won't let you down