My colleague is in escrow with a client who is not late on one mortgage payment and was successfully approved for a short sale merely because he threatened to stop making payments.
But just because you are eligible, doesn't mean you necessarily should. You should reflect on your current situation and decide if you can afford the home you want to purchase if you have a successful short sale. Make sure you get into something that you are happy with and that you feel comfortable with (the loan I mean).
The credit score is not affected by a short sale, as FICO (the scoring organization) has no determination as to any score change in a short sale situation. Any that is a verifyable fact.
Additionally, after a short sale, you are IMMEDIATELY eligible for a Fannie Mae mortgage. Even if Fannie took a loss on your short sale.
BOTTOM LINE - Do a short sale, make your payments without going over 30 days, and your credit is not affected at all. Just be careful and prudent when you hire an agent...many now PRETEND to know about Short Sales, as demonstrated by the previous answer. Find someone that really knows.
John & Sarena Villaescusa
Keller Williams Realty