Farming, Villagers, & Grinders
Discounts and zombification
Even though the server difficulty is "Normal," villagers will be zombified no matter what. This makes it easy to get discounts and set up a lot of villagers.
You can only get a discount once. Zombifying villagers multiple times won't give you a better discount.
Access
If you have villagers inside your claim, anyone can trade with them. If you want to keep them private, a good idea would be to physically block them off. Untrusted players are still unable to open doors, so it's easy to deny access. You could take advantage of this, by, for example, setting up a secure room on your claim and requiring someone to pay you to use your villagers.
Spawners
Spawners are mineable on the server. You can also buy them from The Apothecary at spawn. You just need a silk touch diamond or netherite pickaxe to mine them. You can use spawners to make farms or mob grinders for yourself, or you can even charge players to use them. See this page to learn about player warps.