The choice is yours but I think your instincts are correct. The guy sounds a little amateurish, he also sounds like he's pressed for cash, so even if he's well intentioned he could be incompetent and the result will be the same, you won't get paid or it will take for ever and be a huge hassle. I don't understand why the builder is on day rates and you are on a lump sum. I don't understand why he suddenly needs temps for work tomorrow. Where is his programme? You now seem to be facing a 7 week lead in. What is the total length of the programme from start to finish, as this is the period he wants you to finance him essentially. As I said it is up to you and good luck, but I don't think this guy knows what he is doing and that kind of person normally runs into trouble, which won't be good if he owes you money.