typically, i bid jobs after work so am usually in my whites. i never seem to have a problem sealing the deal.
however, i prefer business casual. nice jeans or khakis (not suit/ dress slacks) and a collared shirt.
i have learned that you don't want to project that you are living too large or have too much overhead.
i was working in a flip house once and a conteactor showed up to bid on the windows, siding, and roof. he rang the doorbell and the HO took one look at him and told him no thanks. the confused contractor inquired as to why he didn;t even want to hear entertain his bid.
**the HO looked him up and down observing his "overly professional" appearence with his laptop and Gucci shoes. the HO then looked at his brand new RAM 3500 dually diesal truck with matching 24 ft equipment trailer and said this.... "I am not interested in paying for your fancy outfit, computer, or $70,000 rig sitting in front of my house...no thanks"
so, I show up clean even if in whites, with a clipboard, and talk like I know what i am talking about.