"Buys out" and "owns" apparently now mean the same as "rent for a small period of time" ...

It’s common to say buying ad space. You have probably regularly heard an advertiser “buying a full page”. No one’s ever “bought” the whole thing, so the confusing language of saying “buy” in this context never came up before.

It's the physical bits of page space in reader's hands, in this case. The usage is pretty common for print ads.

I thought either this, or GE provided all of the content for an entire issue. I don't think I've read more than one or two physical newspapers in my entire life (I'm 34), so maybe "buy out" is some term of industry I'm not familiar with that makes sense to others who do read newspapers?