My understanding is they are very efficient in moderate climates but in areas where you have extreme temps, they may not be as effective as you want.

My questions are:ABOUT 1013 exchange : I understand that I have to exchange a two family for a two family, but if I buy a two family and make one of the apartments my primary residence, will I still have to pay capital gain taxes if I sell in let's say in 5 years? 

I don't want put all my energy into chasing the money, so I understand to trust the process. 

Make sure on your rental agreement that people understand they are renting a room with shared access and responsibility for the common areas.

Without that experience it will be hard for them to truly understand and fight for your unique and specific needs as an investor.

Wait a bit to understand how your property performs and readjust your strargey for next one. 

I bought my home at $100K below the mortgage owed, and it was an REO for 3 years.To understand why banks are so cautious, I learn from my wife it's an anti fraud thing.

As a side note, I understand that you may identify up to three (or more) properties with the intent of only closing on one of them.

I don't have many contacts in RE in the area, and I would like to speak with someone who has a better understanding of property prices in Fairfax, Prince William and Loudoun County.

I would make sure they understand you are taking on the burden of fixing up the place, and I would be buying it now before they spent all their time and energy getting it fixed up...The more time and money they spend the more they will expect at the point of sale.