We own three, on the same street, they are called 1/2 duplex here. Definitely worth it IMO, with caveats. The first one, the roof was bad, but the design is that it's basically a townhome with a garage next to it, so only the two garages shared a roof or wall. It was so old there was no weaving a new roof into his. He didn't want to reroof, we asked if we could roof the entire garage as we truly had no other options. On OUR dime, about $1800 we were offering him. He said no, so we were considering at least replacing the roof on the rest of it. And investigating other ways to separate our roofs, but all would have needed his OK. Then the rainy season came (he was also a new owner) and rain was coming in through his light fixtures. Suddenly he was willing to reroof. He wanted to go with the cheapest guy, I didn't (been down that road before), again offered him the price difference, about $2K. For some reason he decided to just pay his half on a reputable roofer. The next two properties we made sure the roof was newer, and I've made overtures to both owners that when they are willing to sell, we'll be here. I would far rather own both halves, it's just not a thing here.