How to tell if a cat is a stray or outdoor cat?

Abby

So i live in a apartment complex and I’ve seen many cats roaming and I fell in love with one it’s a female and I think she’s had some litters but she’s soo sweet I’ve been feeding her cuz I can’t help it , she’s charmed me I would love to keep her cuz I’m moving when my lease is up she doesn’t seem to skinny, but I can’t really tell tho cuz she has a lot of fur but I don’t want to steal a pet .. she also won’t come inside my apartment either, although she’ll follow me right up to the door then stop .. so how can I tell cuz I don’t think anybody here would chip them and I live right next to a sub Division but I really love this cat already.