The only things that aren't set in stone yet is the setting, and the purpose of breeding/selling monsters. A farm and town style setting like in Breeding season is only place holder for now until I think of something better.
Again, a silly idea thrown around. Feel free to ignore it, if it's too cumbersome or you don't like it.
Basically, different people need different monsters, and they use them for different purposes (not only for kinky play purposes).
For example,
hunters or guards may need wolfmen with certain level / traits
farmers may need bulls (farming) and cats (pest control)
brothels may want elves or the like... because elves.
A noble may want a dryad to be a sentry for his forest... and so on.
The monsters you actually "sell" to the inhabitants become actual NPCs and you can find them around the town/city (I guess they won't talk, though).
And in any city there is only a certain number of "slots" you can fill. Once you filled all the slots, you can move to a different town, and you can also find new monsters in the surrounding area (you don't need to literally move your whole farmhouse around, you just discover a new location once a certain number of events are triggered in the previous one).
As you discover locations and new monsters, new events unlock in previous locations (for example, farms that previously bought cats, can commission you bulls once you got ahold of some) or randomly some monsters may get freed / run away / get lost, so you can sell another monster to a previously satisfied customer.
While I would preferer a debt repayment to not overbearing (if exists at all), I guess that a generic reselling system (like Breeding Farm or just simply resell your trained monster to a monster seller) can be included alongside the main one, to make some cash along the way.