Does a Hidden Meadows property with a guesthouse need two separate HVAC systems?
Usually yes, and it's typically the better approach rather than trying to run one oversized system to cover both structures. A second smaller system for a guesthouse or casita adds $6,000 to $12,000 depending on size, but keeps each space properly sized and lets the main house and secondary structure run independently, which matters if the guesthouse is rented separately.