My little brother was wanting to get a netbook and ebay had listings for $100 android netbooks. His main use would be facebook and runescape. I was wondering if an android netbook can even run runescape.
Huh? Android can run flash no problem. You must be thinking Ipad.... nevertheless you get what you pay for it. I would NEVER recommend to anyone buying something like a laptop for $100. It's a waste of money and you(your brother) will be only disappointed. Rather save a bit more and buy something he can actually use for 2-3 years.
Why don't you link us what he wants to buy. Again though, I would say rather save up some more cash, and buy something decent that he can use in the future as well.
Honestly I wouldn't buy that. It looks cheap and it's uses are really limited. You can get a refurbished netbook for around $200 (search the mayor manufacturer sites like hp, toshiba, dell and others for "refurbished"). These have a decent battery life, warranty and can be used to run other stuff too.