I'd recommend mastering VFP and VB. You should also get very familiar with HTML, vbscript, javascript and OLE/COM. I have a full time job plus consulting, and make more consulting than I do at the full time job. However, I plan to retire from the "full-time" job in four years, if I don't drop dead first. I can then move into seeking out more clients -> more money.

My suggestion is to try to find someone who needs part-time help and build from there. Start with a VERY fair price for your work, and as you hone your skills, expand you client base and raise your rates. When you get to the point that you're working all the time, raise your prices.