If my husband bought a house and I'm not on the deed, what happens if he dies?

The house would be part of the deceased husband's estate. First the estate must pay off any debts, so that might mean the house would have to be sold to do so. If he had a will that included the house, the will would control. If he did not have a will, the state's instestacy laws would control (which generally give the surviving spouse at least a 50% share of the estate). If the wife obtained the house through either of these methods, she could attempt to talk to the mortgage company to assume the debt, but it would be subject to their agreement.

Assuming the husband is still alive, you don't need an income to be put on the deed, if the deed is legally in your possession (that depends on the mortgage laws and practices in your state). Otherwise you'd need the lender's persission. You can pay the mortgage, but to actually be on the mortgage would require agreement by the lender and almost certainly regular income - it would be nearly the same as you applying for the loan separately.

You should really talk to a good estate lawyer in your area to be properly prepared to handle these eventualities and get advice specific to your situation.