Treating more pets
You need to treat Hillary Duff's pet good if you want to have more people bring their pets for you to treat.

Sicknesses

Type	Length	Cure
Broken leg	5 days	Put bandage on and let him or her and rest a lot
Flea	3 days	Wash him or her with an anti-flea shampoo
Flu	3 days	Flu medicine for three days every day one time
Item swallowed	Unknown; as long as it takes for you to extract it	Buy an Extractor and extract the item from the pet's belly
Ugly	Unknown; as long as it takes for you to make the pet beautiful	Comb his or her hair and put some clothes on
Worms	3 days	Feed him or her anti-worm food

Cheap food
The first thing you can do is just cook eggs. Stay with it. It is just as effective and it costs more items to make harder food.

Free item
If you are treating a pet for swallowing something, extract the item from the belly and get a free item. When the owner comes the next day to pick up the pet you get will get money plus an item.

Pet in inventory
Open up the cage that your have your pet in. Tap your pet and select "Put in inventory".