How can you compare a complete house to a pool, that's what people are shopping for. My wife had a pool at her house and I would fill it in with dirt myself before I had to deal with that headache. That's like saying, my house has a motocross track in the backyard and I am complaining there is no value on the appraisal. I can assure you, 99.9% of the people that have seen my house, like the guest house, no love the guest house, it is handy if a family member is being taken care of, a teenager who needs or wants their privacy or friends spending the weekend. The electric bill runs $15.00 a month when no one is staying there. I would think that is a bargain just for the small chance you need an extra place for someone to stay, also it keeps you from having a higher a/c or heating bill because you have 600 sq. ft. less to cool or heat, instead of cooling a 2600 sq. ft. all summer, you only cool 2,000 sq. ft. All I can say, is when I purchased this house, I was single, my son lived in the guest house, I lived in the main house, he had his privacy and I had mine. He would have his friends over and I was never bothered as I would have been if they were in the room next to me. There are a lot more positives to having a complete spare house than a pool. Another thing to consider is people commonly add rooms over their garages, I would be willing to bet any of them would take having a separate house built with a full kitchen and bathroom over a space added after the house was built. As for taxes, they are the same, 2,000 sq. ft. plus 600 sq. ft. in two houses or 2,600 sq. ft. in one house, they are both finished sq. footage. Also, I don't think building separate guest houses is common because it is a lot cheaper to build one house than it is to build to completely separate houses.
