I rather like the different colours and patterns beasts can come out with and am wondering if I can treat raising beasts as a trade. Is there a market for fully grown (and fully fed for reagents) beasts? Would I at least break even when the beast is sold, or will stable fees nix that?

In short: no.

If you have something -really- unusual, it might go for a good amount, but everyone will try to cheat and talk you down, and you will spend ridiculous amounts of zimoru to get there.

Beast experimentation is hobby only.

Aww.
Thanks for the quick response!

Trust me, I've tried. You'll be outdone every time by collars and custom beasts, and the fact that people can just sit around and wait for your price to drop while you spend more and more on stable fees.