When I started my painting company I just opened a charge account at a paint store and charged things for jobs made sure to pay everything on time and soon I had accounts at four differant paint suppliers and could get larger tools (sprayers,ladders,scaffolding,ect).the key is smart small if possible and make sure you pay everything on time........
If you are talking about credit as in getting loans, credit cards, etc., you hve to show that you are making $$$ by filing your sales tax forms, income taxes, etc.