Do note that the SEC's argument is usually along the lines of "if anybody is buying this to make money, then it is potentially a security." The "common enterprise" part makes it a bit different, but only a bit.

Also note that time shares typically are securities, in my understanding. In contrast to a house, which is not. My argument there wasn't to identify some other things that are or are not securities, but "things that are kinda useless." In the case of timeshares, I'd say they are actively more harm than good.