A card or two, will not kill the deal, as long as he has good credit. I process loans every single day where people have opened cards in the months, weeks, or even days before (heck I recently had one buy a boat, and another bought a dang house in the middle of our process) a mortgage application. As long as he has a good score and can qualify with all the payments, it will be fine. I would not go crazy and get a bunch, but one or even two will not hurt him. Biz cards obviously won't show at all, but the inquiries will. But if you are looking at a year out he can easily get a couple of cards and a couple of inquiries with no ill effects.