When I was freelancing on the side, I used to think that $50/hour was on the high side, but it's actually on the low side. You should charge at least $75/h if not $100/h.
Don't believe me? Consider: Barely anyone works 40h/week of billable time. Most full-time freelancers bill 4-5h/day and do non-billable work the rest of the time. That's 20-30h/week of billable time about 50 weeks of the year. Say you bill 25h/week for 50 weeks, and you want to make about $80k. That comes to $64/h, and that doesn't even account for your expenses!
Here are some resources on freelance benchmarks and rates.
I'm a freshbooks customer who's also an ex full time freelancer. I agree with sunir. If you can follow through on your work, you're ahead of the game. Consider your target demographic and how they consider paying for things. I do mostly systems administration and web programming these days, but I have a strong IT background, if I have a client that I want who's on the fence about if they need me, I ask about their monthly costs. Usually they're paying way too much for telephone, internet, email etc. I can usually get them to leverage my price against a year of overpaying for services, but that's just part my pitch. Which is a slightly different topic.
The point is, you're worth spending the money and if they're paying you enough they're worth putting in extra effort. It's mutually beneficial.
Don't believe me? Consider: Barely anyone works 40h/week of billable time. Most full-time freelancers bill 4-5h/day and do non-billable work the rest of the time. That's 20-30h/week of billable time about 50 weeks of the year. Say you bill 25h/week for 50 weeks, and you want to make about $80k. That comes to $64/h, and that doesn't even account for your expenses!
Here are some resources on freelance benchmarks and rates.
http://www.freshbooks.com/reportcards/all-industries.php
http://freelanceswitch.com/rates/
(Disclaimer: I work for FreshBooks.)