I'm not a contractor, so some flu time off would suit me just fine. I get paid whether I show up or not.
However I suffer from a very strong immune system, so I get stuck having to work through the whole winter. I exercise a lot and take vitamin C. My favorite concoction is Emergen-C (http://www.emergenc.com/), which is basically the same thing as Airborne except comes in a powder that you don't have to wait for it to dissolve. It hits your system like a ton of bricks and really boosts your immune strength.
You can also take vitamin-C pills throughout the day, but actually the best form (besides emergen-C) is powdered vitamin C. I think they call it "crystals". The pills don't always dissolve well in your body, the powder is readily absorbed.
Prius or Insight as far as hybrids. Non Hybrid I would look at a Toyota Corrolla.
You don't want any car that doesn't get close to 40 mpg highway.
If your spending a lot of time sitting in traffic bumper to bumper go with a smaller Hybrid.
Been caught in that DC rush hour traffic a few times and it is not fun.