The 300k fee is the cheaper alternative for people. Collectively obtaining 2mil for an FC is rather easy (I can almost afford 10 of them by myself). You can't be kicked from the FC while having a room associated to a house, likewise you can't leave an FC while having a room associated to them. You have to remove the room access (though it seems you won't get any gil back in doing so) in order to be booted or leave.

It's about personal decisions more than anything else. As I said, 300k really isn't a big deal when it comes to a long term plan. Occupying a room in an FC is considered just that. Unless you happen to hop FCs frequently, you'll likely get your 300k worth of spending (assuming this sort of side content is your thing).

The cost of personal housing is likely to be MUCH higher than 300k. I'd assume it'd be near the same pricing as FC houses, at the very least the S size ones. We won't have to wait too long for it neither, several months maybe, following 2.3 release.