He needs to go to the vet for a checkup, that is just part of basic care for a pet.
Once a year, heartworm check, etc.
This is a special situation, you don’t know where he’s been or what he has been exposed to.
You didn’t mention how long he was out there. Frequent vomiting and poor appetite are obvious signs of illness. He could be nauseas or in pain, some dogs are more stoic than others and are good at hiding it.
Get him a clean bill of health, you will both feel better 🙂
PS: I’m glad he found his way back to you. But, if you are truly between a rock and a hard place, contact your local SPCA, explain your situation and they will tell you your options.
https://www.aspca.org/about-us/faq
