I think it would be really nice if shared housing allowed for all tenants to count towards its activity.

Is that not how it works with Free Company Housing?

My friends and I bought a personal house together and it is under my name. I'm very active, but you never know when life happens. They paid into the house just like me (though I was the one camping the plot) and I think they should count towards its upkeep as well since they are registered as owners as well. They have all the same permissions as me.

It's not just my house--it's theirs too. Why do only I count? It has their furniture, their gil went into it, and they use it too. Their use should count.