So, here goes, you have done a lot of marketing, you know people and know people, good karma intervened and sent you a client that is ready to work with you. You might not have the product or service ready, there might still be holes and problems in the model, but say yes. Commit to delivering, give the client the confidence you can make it happen, and from the moment they sign, dedicate yourself to solve all the problems. It usually works, and if not, it is probably a business that is not for you anyway.