I would think it's very uncommon for people living in apartment buildings to go to a sauna 4-7 times a week (I believe that's often not even possible due to var

I would think it's very uncommon for people living in apartment buildings to go to a sauna 4-7 times a week (I believe that's often not even possible due to various rules). When you add in that there's some correlation between lack of wealth and living in apartment buildings I don't think you can rule out income level that easily.