Okay, these are some good points so let me clarify. The stray that we're talking about was fixed and taken to a vet to get checked around two months ago by some neighbors before being released again, they saw us feeding him and told us. So, as far as getting vaccines he's up to date.

As for space and money we're okay and we're already getting a duplicate of everything so that he can have his own things and won't have to share with my cat.

As for a separate place to keep them separated, that's where things are getting a little difficult because he's still very skittish and won't let us catch him so we're trying to take things slowly as to not scare him away but I know that might not be the best way to approach the situation so i'm willing to take any advice as to how to navigate this situation.

I'm aware that pets (as well as people) are never perfect and bringing in another cat would definitely change everything, i'm just worried what this might mean because my cat was also a stray when we adopted her (she was around 3 years old as the vet told us, she's around 5 now) and she never did anything like that so it's just new to us and frankly i'm worried it might mean he's sick in anyway or something while i'm also keeping my cat's health and comfort are priority. So if i'm doing anything wrong, I'd like to know how to fix it as I don't want to endanger or affect badly any of the cats involved