Cats gotten from various locations can have issues... The important thing is to do your research...
- Know what qualities you want in a cat/kitten (active, or less so, friendly / cuddly or more aloof, vocal or not, long hair or short hair)
- Know what signs mean an unhealthy cat / kitten...runny or closed / squinty eyes, anal discharge, lethergy, bald or irritated spots or areas, sneezing, hacking cough, etc.
- Find out what your options are...If you want to adopt a rescue, look for local groups that are independent and /or at local shelters, also find local reputable breeders if you are interested in a purebred (many breeders will also have retired adult cats for placement as pets after they are neutered).
- Find out what each "source" provides...do the shelters (or breeder) vaccinate, health screen / vet exam, spay/neuter, etc. Do they do any temperment testing on their cats or foster them (kept in a private home awaiting adoption). Also get references from rescue groups and breeders.
In my experience....I've adopted one adult cat from a shelter and 2 feral kittens off the street.... All had their issues...The cat from the shelter had an underlying heart condition, seizures, and now allergies. The ferral kittens I had to pay for spay/neuter, rounds of shots, and then treatment for eye infections and UTIs. I do not blame the shelter (the cat had no visible symptoms at the time and the enlarged heart wouldn't be uncovered in a standard vet exam). BUT, I will say that WHEREVER you get your next cat, take them to your vet ASAP for a thurough health screening to detect any problems the shelter, rescue, or breeder might have missed.
For myself, now that I have three rescue cats, I'll most likely be looking at buying a kitten from a good breeder or adopting a retired breeding cat for my next addition. That said, I'm a sucker for cute cats in need, so I might end up falling for another feral or shelter cat (which is why I should NOT go to petsmart on saturdays when the shelter groups are there).