I guess everything is common among rich families
I've come across this a few times, however in Warsaw, most people don't have the space in apartments. Though there are new build apartments that have staff accommodation and some of the newer houses in the suburb where I live have dedicated staff accommodation and sometimes security lodges.
Some of the Warsaw elite decamp to Sopot for the whole summer, often renting a separate flat for the nanny and the kids.
digital snowflakes
Most of those are over 50.
Not sure if it's going to benefit the parents and the society though.
I think so too. It's storing up problems for the future. After capitalism started to intrude into Poland, a whole generation of kids grew up who are exceptionally materialistic and transactional. There needs to be far more group activities, far more activities where there's no profit involvement.
We've even had people on PF pushing for-profit summer camps when many decent voluntary ones exist.