I supplement my income and since you're an independent contractor you get to take some very nice tax benefits. Also...I have been able to deduct some purchases, mainly equipment, that is used for business purposes.
In order to really make some money, you'd have to dedicate your time like a full-time job, be aggressive and know which jobs to take and which ones really suit you. I have tried a w-i-d-e array of jobs and have gotten into a groove of exactly which ones I really enjoy doing.