The only suckermouth catfish that sell regularly, are the bristlenose catfish and its colour varieties. Most other suckermouth catfish aren't big sellers due to their high prices.
If you are breeding fish at home, then keep bristlenose, some livebearers, a few of the more colourful rainbowfish, Apistogramma cacatuoides, and a few of the less common suckermouth catfish like Farlowella, Loricaria, Peckoltia sp. Corydoras also work. The less common fish don't breed as often and can usually be sold readily if you have good prices. The other fish are your bread an butter and you breed as many of them as possible.
Years ago I used to supply a number of pet shops in Perth with rainbowfish. I sold mine for $2.00ea, which was about 1/4 the price of what the eastern states wholesalers were selling the same fish for. I did it to drop the price of them because they used to sell for $20+ ea and very few people bought them. After I dropped the price and made them affordable to the average person, the shops started selling heaps. I wasn't in it for the money but I covered costs and made a few dollars even selling them for $2 ea.
Basically if you can supply unusual, interesting and colourful fish for a reasonable price, you can sell a lot more of them.