It depends on quite a few factors:
- How much experience do you have?
- How much available time do you have?
- What do you like doing?

If you can't commit full time to a project during the week because of school, you can focus on one element of a site design, and outsource the rest.

Will you be customizing existing themes or writing new ones completely from scratch? Pricing will vary based on all of these answers, and it's a broad spectrum.

I recommend some of these resources:
http://chrislema.com/tag/pricing/ (he's on Clarity too and you could chat with him)
http://www.winwithoutpitching.com
https://www.freelancelift.com

I also recommend figuring out the ideal rate for the lifestyle you have or want: http://www.yourrate.co.

Good luck - happy to chat more if you'd like!