I've tried asking if the land's still available, but again the dialogue tells me the sale is being made, but the state of the quest doesn't change. The "Is that land still available" option remains, no money changes hands, and the objective to visit the site never come up.
SetStage BYOHHouseFalkreath 100 does nothing. It doesn't re-run the script fragment that was supposed to set the objective, and enable the building site stuff. It looks like the fragment didn't function the first time, and now can't be re-done. Anyone know how to force it forward without breaking anything more?