Mortgage companies typically use the mid FICO score.
Your husband's scores are very low. You would have to have a big downpayment and no other debt to maybe qualify for a very high interest rate.
Get a copy of his credit report and start working on fixing the negatives. First, pay off current credit card balances. Carrying balances of more than 30% of your available limit kills your score. Paying them down will give a quick boost to his score.
Second, start contacting the negatives, newest one first and work back to the oldest. Ask for delete for payment -- some will, some won't. The older the debt, the more likely they will settle for less than full balance. If the debt is older than 3 years, offer 25%; 2 or 3, offer 50%; less than 2, offer 75%. Lump sum payment gets the best deal. Payment plans have to be short term.
Get any settlement agreement in writing and keep it along with your payment proof, forever. Don't give the collection agency direct access to your bank account.
Paying off old debt won't increase your credit score (unless you get the item deleted); however, paid debt looks better than unpaid. Mortgage companies will require you to settle old debt before approving any mortgage.
You should also put a set a mount in a savings account every payday toward the downpayment and closing costs.