Overall, the rental market in Ashburn is still very good. Will you break even on your investment property, is the big question, or do you want to?
Breaking even does really does depend on multiple factors: HOA, RE Taxes,and maintenance. For example, if there are high HOA dues, that should be absorbed by you, which could put you into the red.
My two cents would be to wait just a little longer and find yourself a foreclosure ( I am expecting them to begin hitting between now and January), purchase one of them at a lower price, thus having a lower cost basis. You then should have a much better chance of breaking even on your investment property. Just watch out for the HOA dues.
Also, it seem every year our Real Estate taxes in Loudoun have been increasing, so you need to be aware of that as well. Our taxes have increased by almost 50% over the past 7 years.