and..you want to make sure he has a complete physical and you need to make sure the bitch you are breeding him with does to..ask the owners for proof from the vet. Dogs carries STDs too.
With labs we have the hearts, hips and eyes certified.( done at age 2.) .I don't know what they suggest for chis..but you want to make sure both dogs are in perfect health and will add to the betterment of the breed. Having a sweet dog is not a reason to breed IMHO
Similar certifications should be done on breeding chi's including cardiac (heart), OFA cert's (hips, patella's, elbows), and sometimes Baer (hearing). Although deafness is not a common illness in our breed it is done by some as a precautionary measure.