Moving from NM to CO, we went from owning to renting, and from a four person hot tub with 240v heating, to a 110 volt, 6ft (exterior measurement) round inflatable. The missus uses it for "thermotherapy" to ease a variety of pains; I keep it up to speed, but there is room for both of us to sit comfortably in it.
The Saluspa brand is the same model as several others with the same dimensions and features. I was careful to order the rubber-bottomed felt pad to protect the bottom of the hot tub. We placed it on a concrete patio. Assembly was very straightforward, but it's easy to misunderstand a couple of steps along the way. It helped to look at a couple of You Tube videos.
Performance: because the tub holds about 175 gallons of water, it is not hard for the 110 volt heating pump system to keep the temperature at 102 degrees. It was also robust enough to withstand a night in the upper teens, though I did cover the heating unit with heavy duty moving blankets, and once it rose above 40 degrees, I removed them. The water temp dropped to about 85 degrees overnight, but the high quality of the materials easily handled the stress. I use bromine instead of chlorine to reduce stressing the materials, and everything else about the care of the water is straightforward. I am exceptionally pleased with the adjustment to the simpler design of the Saluspa. Good air bubbles, too.
The value is spectacular. If the inflatable tub lasts two years, the operating cost would still be about half of that for the care and feeding of a larger, permanent one. If you can be happy with a two person 6-footer, I don't see a better better benefit/cost ratio anywhere. I believe the round model, at just under 8 feet in diameter would indeed the needs of four people at the same time.
Last thing: The height of the tub enables the missus to step into and out of it with no problems. The control panel is reasonable and has a safety setting to lock it from kids messing around with it. The lid is easy to remover and has six straps with snap locks that require three fingers to open it. I recommend getting three key-lock replacements on alternating straps to secure the tub from unwanted users. Pay attention to the safety warnings about electricity risks--the tub is safe when used properly with respect, as is true for ANY hot tub.