How do you protect kids from a wood stove that will not be in use without spending a fortune?

There isn't a big danger if it isn't in use. The only danger would be if they fell and hit themselves on it. You'll just have to watch them carefully around the wood stove and teach them not to run around it and to be careful. Kids can learn at a really young age the proper behavior around different things or people.

Secure the door with a plastic wrap and tie it well, to prevent anyone from opening the door.