A 6 person sauna is where a home cabin stops being an appliance and becomes a small building project. The heater is close to commercial specification, the circuit is substantial, the footprint needs a dedicated site, and heat-up times get long enough to change how the thing is used.
The heater and the circuit
Six seats means a large volume, and a traditional heater for it is a serious piece of equipment on a dedicated high current circuit. That is a licensed electrician, a run from the panel and possibly a panel upgrade. Get this quoted first: it is the line most likely to make a six seat cabin impractical in an older house.
Heat-up and how it gets used
A large cabin takes considerably longer to reach temperature and more energy to hold it. Owners of six seat cabins plan sessions rather than taking them on impulse, and tend to use them less often and with more people. If your actual pattern is twenty minutes alone before work, a smaller cabin will get far more use.
Where it goes
Almost always outdoors or in a garage, because six seats plus benches on three walls plus heater clearance is a room rather than a corner. Outdoors it needs a base sized and drained for the loaded weight, setbacks from boundaries, and in most places a permit. Plan the base before the cabin arrives, not around it.
Bench layout matters more at this size
Six seats can be an L, a U, or two long facing runs. Facing runs are sociable and let two people lie down. A U seats the most and lets nobody stretch out. At this size the layout is the purchase decision, because the difference between a room for a group and a room for a family is entirely in the bench plan.
Questions people ask about 6 person sauna
Will a six person sauna work on a normal panel?
Often not without checking. A traditional heater at this size needs a substantial dedicated circuit and sometimes a panel upgrade. Price it first.
Indoors or outdoors?
Almost always outdoors or in a garage. Six seats with benches on three walls and heater clearance is a room, not a corner.
How long does it take to heat?
Long enough that owners plan sessions rather than take them spontaneously. That is the real trade against a smaller cabin.