I think it is probably an achievement that is no longer possible to get. The achievement is for purchasing your first home, which is how we got houses before the big housing revamp this spring. Now you're given your house automatically when you start playing, so there's no need to buy them. :D
Suggestion: put a tag on these older achievements to mark them as "retired" or some such. (Or take them out of the encyclopedia and make them "hidden" achievements.)
Or just give people the achievement after they customize their houses. I'd rather see the requirements modified than see the achievement be made un-achievable.
I'm working hard on getting my last subway badges. I heard that the subway was "not long of this world". If there is a nat-ur-al disaster that destroys the subway maybe badge could still be obtainable by doing restorative work of some sort?
But there are already achievements for customizing your house. I've never been someone who can/will grind for currants, so it took me a while to buy my first house post-reset and then upgrade to an even bigger one.
It's a trade-off: houses are given immediately now, with no work or currants required (and I think this is a good thing!), but that's one less achievement to get.
Teresa, the hint was given that the subways are not ideal, but unlikely to get removed, more likely improved, better interlinking between areas so you don't have to slog around half the map