It's not that old that's why it's not that valuable if you sell it. But you could still try and look for a collector and maybe they could buy it for a small price. Or you could give it to me. Just kidding. Why not keep it? Put it on a time capsule. After how many years you could get it and remember your memories with it.
Depending what country you're based in, there are options - where I live there's a site called Gazelle that accepts phones. Where are you based? It might make it easier for me to offer suggestions if I know what country you're in.