When I first set up a tank of my own in 2019, all I wanted was a little guppy colony tank with live plants and maybe some shrimp. But knowing what guppies are like, since my parents were in the aquatics trade for decades and had a fish then a general pet store, and always had a tank at home since I was a kid, I knew guppies breed like wildfire, so I checked with my LFS if he'd be willing to take the young ones before I brought any guppies home. Luckily he was, since most chain stores won't take fish from home breeders, especially livebearers, and not all privately owned LFS will either.
He was fine to take them once they reached around three months old, and old enough to sell. Said he couldn't pay for them since they're a cheap fish, but might be able to give some store credit here and there. Since I got into breeding them for a while, I ended up bringing in bags full of young guppies, mollies and platies pretty regularly, earned the nickname "The Guppy Girl", but built a relationship with the owners and staff over that time, chatting when I popped in, and he'd knock some money off of my bill since I'd always be buying something anytime I went in there anyway. In time he came to know that the fish from me came from healthy tanks, had nice colours and sold well, and he was happy to add them straight to the sale tanks with other fish once he'd had a lot of fish from me and knew they'd be disease free.
Once my cories started spawning and I was getting an overstock of those, he said he'd pay for shrimp and baby cories, and really wanted any pygmy cory fry I could get him, since they're popular and sell well. Said he would give me some cash for them. Not a lot, since they're not particularly expensive either, but more valuable to him than guppies/mollies/platies are. I needed him to take my overstock of livebearers much more than he needed the fish! So I never asked for money, and was just grateful for the times he did give me some store credit.
It really would be fruitless to try to breed to make money in just normal home tanks. What is very useful about doing some home-breeding and either selling or giving away the stock, is the connections you can make that way. Due to my relationship with that store, he helped me out when I needed someone to house a big batch of juvenile fish that were too young to sell, I met other local hobbyists through being at the store often, learned a lot from chatting with them and the store owner and staff, and networking with other local hobbyists is invaluable.
Through selling batches of pygmy cories and some excess live plant trimmings privately I've met several great local hobbyists, and traded for other fish and plants I really wanted to keep. Another man I met that way is an incredibly smart and connected fishkeeper who is involved in the tropical fish club for my city, so he has a lot of connections to help source other, less commonly sold fish from the people he knows, and has given me fantastic advice and become a friend.
There's no way even with rarer and expensive fish and four tanks that I could sell enough to cover the cost of running the tanks, let alone raising the fry for months, and the idea of profit is a laugh! Privately owned fish stores operate on a knife edge, are being outcompeted and shut down because of the big chains, people buying equipment and food etc on Amazon instead of local stores, and it's incredibly hard for them to even stay open now. My one that was generous has shut down now.
Breed if you want to, because it's fun and a great experience, and it's nice to at least offset the costs a little when you sell some young, since it's an expensive hobby. But also try to support your LFS where you can if they're an otherwise decent store, and try to understand how thin a margin the LFS have now. Their overhead costs are crazy and they're dying off, which would be a real shame if we're left with only soulless big box stores and uncaring massive corporations.
