I would sit down with a lender & discuss your options.
The Marie Souza Team - Top Selling on Cape Cod
Cape Cod Real Estate Services
How's your relationship? If it's too cozy you wife will be jealous, and if it's to confrontational you'll want to hang yourself. Is there a basement where you can lock them up if they decide to move in? This is important in considering your dilemma.
A non-occupant co-borrower (NOCB) is effectively the same as a "co-signer" and what is important to note is that a NOCB cannot negate bad credit. This means that if your credit score is not sufficient to qualify on your own, there is nothing a NOCB can add to fix that. The only thing a NOCB brings to the table as far as qualifying is their income which can reduce debt ratios.
If you have a credit score of 580 or above, FHA allows a 3.5% down payment and your parents can be NOCBs if needed. a NOCB does not add any extra cost to the mortgage but does saddle your parents with significant liability. consider fixing your credit and waiting until you can qualify alone.