Instead of buying animals in Rune Factory 5, you are going to need to get monsters to produce common items like eggs and milk. One of the staple monsters you will want to have on your farm is known as the Buffamoo. Luckily, finding and taming a Buffamoo is relatively easy.
Buffamoo, like the Cluckadoodle and Wooly, can be found in the Phoros Woodlands, and it produces milk. The Phoros Woodlands is an area that you will be able to access from the start of the game, so getting a Buffamoo can be done early on. Buffamoo are extremely weak and can be killed by party members without much trouble, so be sure to go on your own when trying to tame one.
Buffamoo can be poisoned by many items, so be careful what you are gifting them so that they don't die. With a bit of brushing and some basic items like Fodder, it is pretty easy to tame a Buffamoo. Be aware that they do tend to spawn in groups, so you may want to thin the herd before trying to tame one.
For more on Rune Factory 5, check out How to get Fodder in Rune Factory 5 on Pro Game Guides!