An in-ground pool that's an integral part of the aesthetic of the outdoor space will add value to a home, especially if the hot tub is in good condition and has been well-maintained. An old inflatable hot tub or portable model stuck on your patio, however, will not add value and, if in poor condition, could even be a turnoff.
No, an outdoor hot tub isn't difficult to maintain. Yes, it requires regular maintenance, but it's not complicated. The key maintenance tasks include:
Checking and adjusting the water chemical levels regularly
Removing the cover and letting it air out regularly
Draining the water and cleaning the tub every other month
No, you don't have to run a hot tub year-round. While many people like to enjoy the benefits of their hot tub year-round, you don't have to. You can shut it down completely by draining all the water from the lines, removing as much equipment as possible that could potentially get damaged by the cold weather, and draining the water. You'll need to use a wet/dry vacuum to get rid of as much water as possible and to help clean up any mess.