Don't go to Craglsane Cavern. Its part of the Jarl's quest and if you clear it before you get the quest, you won't be able to get the house

I just got the house the last time I played - and became Thane. The most horrible HouseCarl you can imagine comes with it. I may have to ask her to follow and then take her somewhere dangerous - but have to marry first, or her body may show up at the wedding and interrupt it, lol.