If we said "Mark Jones's house is for sale," the "s's" would be correct, yes?

Yes. And there are people who would say just “Mark Jones’ house, just as some would say Jesus’ teaching rather than Jesus’s. Sometimes I think there are too many sibilant sounds when one uses “s’s.” A friend and I differ when speaking of a house owned by Lonnie Andrews.  I just write, and say, “Lonnie Andrews’ house” because I don’t like the zzz of “Lonnie Andrews’s house.” I even write “Leland Fox’ house” rather than “Leland Fox’s house.”

On occasion I used to tell my students to bring examples of incorrect use of apostrophes just by looking at signs on mailboxes or welcome mats. Next-door neighbor has “The William’s” on their mailbox. I wonder which of the Williamses is meant and exactly what he or she is possessing. Take a look at the Christmas cards you get, if you get Christmas cards. My guess is that you will have examples of “the Anderson’s,” “the Smith’s,” etc., etc.

gww