Bear in mind that the community would render aid to anyone who needs assistance in maintaining their own properties as well.

Ah, gotcha, so when my neighbor's house needs to be redone because he rewired it himself, I'm on the hook for that. Too bad I have to stand by and let a couple of transient drug addicts cook meth in the house next door again, after I just spent last year decontaminating it and rebuilding it after the previous amateur chemist stripped out all the copper and dumped industrial solvents in the basement.

You’re also ignoring my mention of the benefit that this mutual aid would enable others to travel to maintained community housing anywhere in the world for free.

Sure thing. That's totally going to happen. Even if this system was in place, how would one go about getting one of thosr places to stay in. Either it's a free for all, first come first serve, with no guarantee that when I get to a destination that there will be a place to stay... Or there is a controlling board with a system to allow or reject people based on criteria set by a small group of people with extra power and leverage over others.

The big problem with the communal house idea (which keeps popping up despite it's glaring flaws) is that no one bothered to examine it critically at all. As soon as you ask simple questions like "who takes care of the empty houses" or "how do you deal with people being assholes" it fall apart into vague handwaving about how everyone will be all helpful sunshine and smiles, which we know for a fact, people aren't that at any level of their being.

I think most people would want to keep their home in good condition...

Except it wouldn't be their home. Someone else built it, someone else maintained it, and after all that work, someone else got nothing for the effort when they had to leave it. Why would some squatter care about putting that effort in, when they can just hop to the next empty house that someone spent years maintaining?