A few pets in Stable #1 Tab #1 are for sale.
All pets in Stable #1 Tab #4 are for sale!
The first 5 pages of the Hatchery are for sale. *

*As of now the first 5 pages are for sale, this will of course not be completely accurate once someone purchases even one pet, since the hatchery auto resorts the pets.

Everything is pre-priced for instant buy, no need to post. If you want to haggle on prices, you may try, but beware that someone else may grab the pet you want while you're attempting to haggle. It's up to you if you want to chance it or not.

I haven't time just now to test and price the rest of the hatchery, I'll try to get to that sometime later today after taking kids to the doctors.