I do not charge for the initial site visit. If its a larger project that will take some time for an accurate number I send them a ballpark number. If the number is in their wheelhouse I start a pre-construction service agreement for a hard bid, engineering, permits and the estimation time. Once the PCSA is satisfied the client owns everything and they can use it for other quotes. They are not stuck using us. So far we have followed through with all projects after that point. This process tends to weed out tire kickers and my number is accurate and firm. I have used this process for my estimators for almost two years now, works great.