Netbook/ chromebook under $250

Since you are looking at used laptops anyway, check craigslist for used laptops. You can find a much faster dual-core laptop with a larger screen for the same price or less.

If you want something small, I'd get a regular netbook running Windows or Linux, get 2 gig of RAM at least though as the lower end CPUs in those are slow.

If this is your main computer, you'll find that the 10" screen is a bit too small, you want a 12" netbook if anything, or at least an external monitor/keyboard/mouse to use at your desk.

Take a look at this model http://shop.lenovo.com/us/laptops/ideapad/s-series/s12, if you can find one around. I managed to buy one for my daughter for $120 (which is a very low price for this thing it should be closer to 160), large screen, great keyboard, light.