Make him PROVE that the HydraBagger works and that it is complete. The deck baffle, the deck boot, the deck to vac hose and clamps should all be there. The bags should not have holes in them. The hood should hot be cracked. The mounting bracket for the vac should also be there.
Do not take his word for anything. Whatever he says, make him prove it with invoices or demonstrations. If he does not own an Op manual, that's a bad sign. How do you look after stuff without one?