I actually have that outside right now… a box wrapped with some insulated tarp and a doorway cut into it, but that won’t do much when winter hits us full force and the snow piles up.
I’m thinking about making a closed off area in my shed with a heat pad to help. I’ve been letting them into my house by blocking off the kitchen so they can’t wander around too much but I can’t leave them there unattended. If I didn’t already have 6 formerly stray cats I could “adopt” them, but 13 cats in this little house would drive us all crazy lol! (never mind the fact I’d have to dedicate an entire room for the litter boxes.)
They’re still fairly small, so I have a bit of time to figure things out and hopefully find homes for them.