I have an annoying problem with Hearthfire. When you build your home in Falkreath territory, you must purchase wood in half-moon sawmill (I don't know if this translation is correct, since in italian version it is called "segheria mezzaluna"). However I have killed all the two owners of that sawmill since a dark brotherhood quest said me to do. The owners should be two vampires, Hern and Hert. But without them I can't purchase wood and, therefore, I can't build my home. So Hearthfire becomes useless. Please help me! Thanks.

You can still purchase wood, it's just the game directs you to those people. It seems most people on the forums are using http://www.uesp.net/wiki/Skyrim:Hod from Riverwood for their lumber. Also, you can actually make your own lumber using the saw mills. Load some wood into the mill and use the lever, you get 10 lumber after the animations are all complete, as opposed to buying 20 for 200 gold from the mill owners.

Yeah, I use Hod too. Wait till he's at the mill, ask him about buying lumber, then ask if you can cut your own. Using the sawmill without asking him that doesn't seem to give you any logs. It's much, MUCH cheaper this way, heh.

And this is available for any saw mill? Whenever I talk to the owners they are willing to sell, but not give away for free. I've also tried getting my lumber through the mill by loading it and cutting myself like above mentioned, but no indication of receiving lumber is seen.