I don't know about commercial property finance, but one idea worth exploring would be to see if you could remortgage your home to get part of the money?
Does it really make that much difference whether he uses his home or not? The bank could still register a judgement mortgage on the family home if the debt on the commercial property is not paid, regardless of whether the family home is mortgaged or not - right?However, I would try and avoid using your own home, if possible. It will be cheaper than a commercial loan, but if a business fails or succeed you will still need a home