I would imagine that since your mortgage is secured debt, if you defaulted on it, while they might not be able to take your house, they could take some of your other assets. Namely, your start up.
It depends on where you live, among other things. In some states creditors can garnish your wages. Other places they can't, but they can come after your bank accounts.
I'm not sure about coming after your startup. It seems unlikely to me, but I'm the wrong guy to ask.
