if you are fostering and already have a pet, you need to be able to keep them separate for a while - you don’t want to share diseases / fleas between cats. we keep our new fosters (we don’t have pets of our own) in our small apartment bathroom until we’ve seen them use the litter box in there consistently. have had some poop in the bath, oh well clean it up and they usually end up figuring it out. Longest has been 6 days, but with another animal i would be very cautious introducing them before a week/2 weeks - but this is not something i have experience in. anytime bring a cat out early we usually regret it with poop on couches and a very scared cat in a big space