If you have cash - you don't need to wait at all. But if you are going to use a traditional mortgage through a lender or mortgage broker then the below information would apply.
With conforming (Fannie Mae/Freddie Mac) financing a minimum of 2 years is all that is required. You'll need 20% down, but if the short sale was due to documented extenuating circumstances (medical, job loss, death of a wage earner, etc.) then 10% down is permitted. At 4 years then 10% down is permitted no matter the reason for the short sale, extenuating or not. At 7 years then maximum financing is available (which currently requires 3% down).
FHA normally requires 3 years from the short sale, but can be OK with just 1 day afterwards if you were current on your mortgage at the same of the short sale, your payments were made on time for the 12 months prior to the short sale & you aren't looking to take advantage of declining market by purchasing a similar or larger home in the same area as you short sold. FHA currently requires a 3.5% down payment.
Shane Milne | Lending in all 50 states | NMLS #81195