Questions about land relinquishment & current Shiva server pricing

So me and a friend have saved up about 15 million gil right now and are hoping to nab a medium house from the next wave of residential districts being opened. Though that may be in a future much farther than we originally thought. Considering we've never owned land before, we don't know how the whole "buying from another player" works. Hence, I have a few questions on the matter.

1. Is relinquishing the lot the only way to trade it to another player?
2. If so, what's to stop another player from buying the property afterwards? What's to stop a plot owner from taking the gil and running?
3. If not, then does that mean the original resident can set any price for the property?
4. If a property is relinquished, does it skyrocket back to the initial price when the property originally went live?
5. Is there any valid news of new houses coming out in an upcoming Heavensward patch?