How much can I sell iPhone 4S for?

My brother gave me a his old iphone he has a iphone 5 now he gave me his 4s, it's in good condition, but the volume buttons only work sometimes it's no contract I was thinking 300 it's the blck one, it' looks good

Sell it here:

http://www.gazelle.com/

Even if it's not in full working order, they will still give you top dollar for it, and it's easier than trying to sell it on craigslist or something. I've sold them quite a few of my old electronics, cameras and such. But now it seems they only deal in phones. Which is what you need to sell, apparently.