As mentioned a couple times earlier, there are plenty of areas outside of towns/out in the county that don't require anything more than inspection of the septic and the state typically regulates that, especially in rural counties. This includes most of Montana. Within city/town limits, that's not the case. Even then, it'll vary on what inspections are required depending upon how developed the town and it's code is,not to mention if they have the budget to pay a building inspector. Some folks recognize that as a benefit and prefer to not have someone regulating their every move.