Almost Adopted a Kitty Last Night!

This cute black-and-white furred thing came up to my apartment door meeowing and rubbing up against both my legs.  Usually cats are afraid of me, flinch when I approach them and run away.  I was pleasantly surprised how friendly and openly affectionate this cat was!  I gave her some food, she nibbled on it and eventually ate it, but still kept rubbing up against my legs, indicating to me she wanted to be petted, so I obliged.  She has her claws!  Claws I can deal with.  I want to take her to the vet to make sure she's spayed before I let her into my apartment, lest she spray pee all over everything.  It was late, so I left her some more food and a bowl of warm water.  When I woke up this morning, she was gone.  Guess she just needed a "quickie", a "one-nighter", some human affection, and then she was on her way.  If I see her again, I'll drive her to the vet to see what's up.  If all is good inside her, I'll adopt her.  Or if she needs to be spayed, I'll pay for it and adopt her.  She's a really nice kitty.