For much of Maricopa County, it's going to be 3.5%, via FHA loans. There are still exceptions/deals, but that's a very good place to start/set an expectation. In Queen Creek/Pinal County, it may be possible to use a USDA Loan, with a 1.5% down payment requirement.
All loans, of course, have credit score requirements, and the less you want to put down, the higher your credit score will need to be.
The down payment is a requirement from your lender and is not based on whether it is a short sale, foreclosure, regular sale, etc. Down payments can be as low as 0% for first time home buyers on several areas of Phoenix (yes, we have done several of those lately) to as high as 20% and up for investment properties or second homes.
The down payment required to purchase ANY home, short, bank owned, or whatever, is dependent on the type of mortgage financing/loan that you are using to pay for the home. For instance, if you're going with an FHA loan, the minimum down payment required is 3.5%.
All the best!
If you have any questions or would like to prequalify, please let me know.
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Purchase a short sale you need lender approval via a mortgage broker who will provide you requirements for downpayment. It can vary from 3.5% or more based on your credit scores, debt ratio, employment history, much more.