Good credit is a must as the lender will use the lower of both of your middle FICO scores. You should absolutely speak with a lender who can advise you specifically, but if you want to run a quick test with your cosigner, you can do the following:
Get their total gross (before taxes) income and then total up all minimum payments on the debts that will show up on his/her credit. The debt total of the minimum monthly payments should be under 50% of their monthly gross income.
For example, they make $2,000/month gross and their minimum monthly obligations on items such as credit cards, auto loans, and other debt that reports to the credit bureau is only $500/month. This would give them a DTI (debt to income ratio) of 25%.
If so, you will likely benefit from the income of the cosigner. If they are well over 50%, then they are likely living with the help of someone else and not a good candidate for a cosigner.