I've done the forsworn consipiracy and the No one escapes Cidhna mine and I was still able to purchase a house.
Chances are there are more variables involved with this particular bug. I too did those quests and was high level by the time the Jarl gave me an option to buy the house. Perhaps I had already excepted the ancestral quest from the jarl before completing both of those other quests and thus stil having a reason to talk to him.
Not sure, but something is wrong there and hopefully Bethesda will fix it, luckily the TC was already going to do what seems to solve this problem in the script.