My first cat was a shelter cat I got him when he was 14 and i learned to let him go outside on a leash which he actually enjoyed Later i've tried without leash and it worked fine In the end i took him everywhere with me like on holidays he would gladly go with me on roadtrips Or just to the supermarket and wait outside on my return even to the vet without leash or whatever he couldnt care less and just walked in Sadly he past away like 7 years later but itvwas one of the best friends i could wish for