Houses, from what YoshiP has said will range from cheap to ghastly expensive. So.. "Please look forward to that"

(Beyond buying the house you will also have upgrading the house and filling it up - Seeing as YoshiP has also stated that Houses will get its own expansion packs, he plans this to be big).
Another gil sink that "may" go along with houses is reoccurring fees (rental/upkeep/and or tax) - though I dont believe there was any mention of that so far.
Currently
1. Repairs
2. MW Taxes
3. Materia/melds (if the item is destroyed the money you used to buy the gear / materia turns into a null reward. 100000 gil -> null, is a gil sink XD)
4. (Ammunition seems to be largely going by the wayside in ARR - but it was a gil sink)
5. Foods and other consumables