Revise county zoning to allow accessory dwelling units

This bill requires Montana counties to allow at least one accessory dwelling unit by right on single-family lots, meaning homeowners can add a secondary living space without needing special permits or hearings. The law sets specific rules for these units, such as limiting their size to no more than 75% of the main home or 1,000 square feet, whichever is smaller, and prohibits counties from requiring matching exterior designs, owner occupancy, or additional parking. Counties may charge a one-time application fee of up to $250 per unit but cannot impose impact fees, restrictive covenants, or more stringent building standards than those already applied to the primary residence. The bill also clarifies that existing building, fire, and health codes still apply, while allowing counties to adopt even more permissive regulations if they choose.