Jesus Christ you've made a lot of threads today. I don't think non-supporters should have multiple residences, because being a supporter means you get extra perks. If the perks are given out to everyone, people will be less inclined to become a supporter.
This was already implemented, sort of. A while ago, Aikar made it so that anybody who was a supporter had a type of "Grandfather" perk (I forgot the name) and you get an extra residence if you run out of supportership. Currently, I can claim two residences. (I already own two) I do not think that anybody who wasn't supporter before that was implemented is included.