Yeah, I'd say a few weeks then.
There's not really any rules to fry...but I do have a few tips.
- Keep the water quality good. Daily 20% is okay, but you could get by doing water changes every other day. It's mostly important that there is no rotting food on the bottom, so I'd recommend sand or bare bottom for a substrate.
- Feed them often. 3 times a day at least, 4-6 is preferable.
- They don't really NEED special food...but fry food for the first few weeks is good, then moving onto crushed up flakes. Also, it's best if you can suppliment in some kind of Frozen/Freeze-dried/Live foods. Makes them grow faster.
- Seperate males and females as soon as possible. You don't need the fry giving you more fry every month.

That's what I can think of right now. Will add more if it comes to me.
OA said he'd take some, and I'm going to sell some to my LFS. Have any tips on selling fry?
Go into your LFS, make a really sad face and say "Please, take my fry. I sadly barely have enough money to feed them. I myself have sacrificed eating for a good few weeks so my darling little babies can live. You can see I love them very much, so parting is very hard for me. If you take them, I will love this LFS forever. (Now is a good time to cry) Please, kind people. Take them. (Hand over fry while shaking with sobbing).
Alternatively, you can take the gruff approach:
"Yo. Take these little dudes off my hands or else!"
And last but not least...the flatter and run approach:
"Oh, I just love this LFS! You always have awesome prices, and the staff is so knowledgable. I would shop here forever and ever. However...I did notice one thing. Your Swordtail tanks look slighty empty, but the ones you have look great. Hey, you know what? Some fry would be cute....what do you know, I have some here. (Hand over fry) Lovelyfryreallysweetyou'lllovethembye!
Eh?
Seriously, though, list them lots of places, like Buy Sell and Swap on here, or your local fish swap website (if you have one), but see how many your LFS will take first. It's going to be hard to find people willing to buy fry, most times you end up giving them away for free or next to nothing.