@OmegaGamer123456 as @Sketch793 mentions the Wellness Treats work and also save time at the vets office itself, you mentioned it takes a long time there so instead of a vet's appointment you can just cut that part out and get the wellness treats from the machine to treat a pet without an examination. It's much quicker and once you've been there and bought a big supply of them you don't have to return. All my pet owner Sims carry a supply of Wellness Treats in their personal inventory.
If you add a vending machine at home it needs to be stocked manually by having your Sim create the treats. Or you can buy some again at the vet's office then take them to your new vending machine to stock it.
If you want a quick way to get some funds I usually get a collecting hobby like fishing, harvesting and collecting. Adding a few plants to harvest can be a real money spinner.
Money isn't an issue in my household, don't get me wrong. I actually prefer to use the exam table for the experience of it. It's just a shame I can't because of this darn bug.
Okay, okay, slow down a moment! I don't run a business at all. I use the vet table to treat my own pet. I don't wanna own a vet clinic, nor do I want to move my tenants out of the guest house as that defeats the entire point of my lot being a residential rental. The issue is that the game thinks a residential rental has a business funds account when it doesn't. There's really no solution for it that doesn't involve not using the exam table at home while still renting out my guest house.
@OmegaGamer123456You asked about that point in your first post and I'm agreeing, yes if you wanted to run a vet's office it would need to be on a different lot.
For bugs, we have a dedicated bug section here:
https://answers.ea.com/t5/Bug-Reports/bd-p/The-Sims-4-Bugs
If you'd like to just select New Topic there and fill in a bug template. Following this you may find that this is by design or it may be something that can be addressed. I haven't run into it on a regular residential lot. I am able to build vet skill on my residential rental lot but they don't have a sick pet currently to test it. I can make vet treats though and I've just opened my game to check that, she's creating treats with no problems.
If you can take images of the message you're seeing in your game to add to a bug report it would be helpful.
But for any sick pets in the meantime, the Wellness Treats are a quick solution you should be able to craft those if you don't want to go and purchase them.
If you play on PC there's also the option of looking for any mods to help. There's a mod section here with advice on using mods safely as well as giving the opportunity to ask questions.
https://answers.ea.com/t5/Mods-Custom-Content/ct-p/the-sims-4-mods-en
