I have done and am doing many short sale and live in Sterling VA.
Here are few things and a bottom line that you should consider as far as my experience goes ;-
If you plan on keeping the house you have and renting it ;
In a recent check with similar situation of my clients Lenders Wells Fargo and Suntrust wanted them to have A) Twelve Months of Mortgage Reserve on their current house that they will be renting - menaing - $24000 for your case
B) 4 months of Reserve on New house- assumming your SFH payments are $2500 X 4 =$10000
C) That means having $34000 Cash in Reserve and then Downpayment and closing cost for SFH
D) Then you should also qualify 40% Debt to income Ratio on conv. anf 50% on FHA
If you plan on short sell the house -
It can be done but as far as I am aware you have to wait 2 Yrs. to buy next home and do the right things to build your credit. .
Some of my clients are coming close to 2 yrs of short sale so I would know in real time but so far these were the guidlines I was told. Short sale Only on the credit of the BORROWER not the person on the deed.
I will know better if I know your situation in detail but with the info given here I feel you may want to discuss option with right people before you take your next step.
BTW if you have not owned a home on last 3 years you are considered first time homebuyer.
703 626 3327