I had a friend who did full-time graphic design from home (it was her own company) and it was a bit tricky. You just have to make sure that you put in your time and don't get distracted too easily. She did great at first but soon started staying out and partying until 3am and sleeping in until 2pm. Then she had to cram a bunch of designs in and have them look like she spent days or weeks on creating them. Oops.
But you've got a better head on your shoulders than she did.