Really it depends. I will be in Lorton tomorrow morning and I can tell you first hand..the good properties are indeed moving quickly. These have been single family homes in the 500's. You should get a good assessment of your property...what it would rent for..what it would sell for..and digest the numbers. If you are adequately equipped financially..then I totally agree with Carolyn. The more house you buy now the better your appreciation will be. Additionally I suspect you will stay in a detached home longer than in your townhome. You should also consult a tax advisor to see how the numbers work for you.
I suspect your townhome should sell quickly if marketed properly. Let me know if I can be of assistance. I do have rental property and am happy to share my experience.
Erik J. Weisskopf,ABR,CDPE,CRS,GRI