That’s simple it's all about your competition. I started a business dealing with low voltage and computer networking recently stopped too many hours and was tired of people calling me every time their internet went down...I only network the computers people I DO NOT provide the service for Christ sakes....hehhe anyways
As I was saying what I did before starting out I call some of my main competition acting like I was interested in their services. Asked them for a quote and told them I would return their call if I didn't find a better deal. So if I was you I would drag out the big phone book them you need a 60 square foot wall inside your house painted...They give you a price then let them know you are also interested in getting this 80 square foot exterior wall sand blasted (or whatever) and repainted. Then bingo you have your quotes and your ready to go into business after a few more phone calls. This shouldn’t take more than an hour or two on the phone by the way.
Not sure how business ethical this may be but hey since when have ethics been economical.