i'm doing the same thing. i have about 70 red hump fry growing out until they're big enough to trade. most stores sell these for around 8-10 bucks so you can ask 2-3 for most shops, though prepare to be low-balled.
i watch the slow ones that dont hide enough get eaten.. the rest i watch grow up and then they go in a ziplock bag and a guy i work with feeds them to his sons turtle...
I've been growing out my Convict fry from different broods for the past year and a half, one of my lfs gives me half retail store credit when they're 2"+. The bigger they are, the more credit I get. The most i got was £8 ($16) credit for a 3"+ breeding pair. It's paid for replacement bulbs, frozen food, other fish, etc. so it's been a good little earner. My bristlenose bred recently for the first time, so now I've got 35 little plecos in their own 30" grow out tank, munching on peas and broccoli. Once i get them to about 2"+, the shops'll take 'em. At half retail, that'll net me about £70 store credit - $140!!
Store credit is the way to go!
Remember, you are offering them healthy, local bred fish that are accustomed to the local water conditions and havn't had to go through the stress of long distance transport, so don't be fobbed off with low offers.
i have about 40 convict fry that my local store said they'd take off my hands when they get bigger. i'd try the store first, even if you only get a few bux, its still enough to get some food, or a beta or common pleco or something along those lines. if the store wont take them, put them on craigslist under the pet section.