Are there achievements for the Hearthfire DLC?

To answer your main question; yes. There are five achievements worth 50 points in total, details here - http://www.xbox360achievements.org/game/elder-scrolls-v/achievements/

To correct your assumption, unless you have knowledge that nobody else seems to, the "30 days" that you quote is in relation to xBox exclusivity, and not to availability as a whole. That is, in the first 30 days after release no other platform will have this DLC. It should very much still be available for download on the xBox in 31 days time and beyond!

Achievements

Landowner: Buy a plot of land.

Land Baron: Buy 3 plots of land.

Architect: Build 3 wings on a house.

Master Architect: Build up to 3 houses.

Proud Parent: Adopt a child.