There's an idea! I wouldn't charge $40/hr though, but you can try it. It could be better to start high and get cheaper. To give you some more brainstorming ideas:
I mowed yards. Something you don't want to undercharge for. Spent $35 on a newspaper ad, got 10 customers. Very good income, charged about $25/hr. If I could do it again, I'd probably charge more.
I tutored an elementary school kid in first grade math. We got him from an unsatisfactory to above average in about two months. $20/hour.
I taught a kid swimming lessons. $20/hour.
I started writing for PCMech at this point. We don't get paid by the hour
Thats just to give you some ideas. People will pay for anything that helps them out. Just be careful not to overcharge. Its a good way to build references and build credibility. I could easily come up with 15 references for any application I needed - it comes in very handy. Good luck.