Yup, you have to address it now and get the contract signed. As far as getting half pay and him blaming payroll.... not buying that story lol. I would be worried because that implies that they have no money in the bank until they get paid which could mean continuous money problems. Its one thing to give a client the benefit of the doubt with regard to money when they've been with you awhile but someone new has to earn my faith and trust in them the same way I have to earn theirs.