In my experience treatments are deducted from your veterinary clinic and not your household fund, if you own a clinic, so it kinda works as a supplier. Only if you bring the cat or dog to an npc clinic is the treatment deducted from your household funds. I have a veterinary clinic and have an exam table at my resident lot. My veterinary sim is able to give treatments to my pets at the resident lot, but all treatments are deducted from my veterinary clinic funds not my household funds. Every treatment in the veterinary clinic is usually deducted first from your clinic funds and then your veterinary sim or the npc veterinaries will bill the pet owner. Since it is your own pet, you are only deducted the treatment and not the price a pet owner pays at your clinic. My suggestion would be to own a clinic, and make sure it has funds and veterinaries to run it for you and your sims can give treatments to your pets at your resident lot and the costs will be deducted from your pet clinic.
