I may be wrong, but i don't think altered and street roadster are classes, just styles of cars. Actual NHRA Class racing (such as super stock) only exists at certain tracks throughout the country, and can be a very expensive hobby, requiring extensive travel. If your buddy is just planning to run on weekends at a local track, it will likely just be bracket racing. My guess is that's what he wants to do. Class racing isn't the place to get your feet wet in drag racing. Most start out bracket racing, hone their skills, and some move on to class racing.
Bracket racing is broken into classes (usually trophy, sportsman, pro, and super pro), but most of the rules revolve around safety equipment required for how quick the car runs. If he's building some sort of roadster, he's probably looking at Pro or Super Pro. The big difference is Super Pro allows a delay box.
If bracket racing is what he really wants, there are sections in the NHRA handbook devoted to that. The general regulation section will be mainly what you're looking for. You might want to get in touch with your local track manager, as he can probably point you in the right direction. If he's planning to run 9.99 or quicker, there Is quite a bit more safety equipment required, as well as an NHRA Competition license and chassis certification.
Hope this helps a little. I raced Super Pro for many years, so I'd be happy to answer any other questions.