or if u can't afford that then i would suggest gimp.
I prepare studies in miniature of the final painting I do for clients. I have attempted to do this in Paint and Powerpoint with a reasonable result when modifying an existing example, but was wondering what software would be able to prepare a painterly (as opposed to hard edge flat colour) version of an idea, but enable me to change colours in the miniature later as modified by client (in layers). I'm a newby to graphic software, so don't know which would cover these requirements. Suggestions and experience would be appreciated.