We will usually discuss the potential subject matter and style of art desired and  I quote before I begin. Prices are roughly based on an average furnished. However an original is unique. Subject matter and the style desired will vary according to the "degree of difficulty." 

We agree upon that  price and then proceed after a 50% retainer is received. I keep a  reasonably steady pace doing what I love most. I promise to deliver the painting on time as per our agreement, with complete satisfaction guaranteed. 
I also grew up appreciating deadlines...and will not charge extra.

Portraits are a particularly fond favorite of mine. Any size, and the bigger the better. It's only just a little more paint... which makes everyone much happier to have the painting fit that perfect wall in the room without having to worry about the budget. I don't paint by the square inch.