Help with the cat??

Okay, so we get a lot of cats at our place because of all the out buildings they're always really wild, a week or so ago I saw a really thin cat and it ran away I saw it a few times again but it wouldn't come too me, I saw it the last time and followed it with food as soon as I opened the packet it came to me and was so hungry. I got it another and by the time I got back it had gone but I found it licking itself in an old building it was scared of me but when it was eating I could pet it. It was very run down, I bought some food and fed and wormed it and even removed a tic, another cat had found where I'd be feeding it but I managed to get the thin cat to follow me home.

I made it a litter tray, a bed and a feeding spot and it is now in the garage next to my house it can't come in the house because we have dogs. The dogs are really old. And I reckon this cat has been abused and dumped it's become friendly to me and I have a bond with it I am feeding it up, obviously I can't keep it in the garage forever but I would like it to come back if I let it out, but I don't know a lot about cats, it has been a pet before I'm sure it rubs on me and has a lot of love to give, but if I let it out when do I do it ? Will it come back for food ? What if it doesn't ?:( help?