Definitely not.
Even though travel time is short it is still far by Swiss standards. Moreover, he has to deal with cantonal authorities (Auslaenderkontrollle) and on that level there is not much sympathy for a foreigner who commutes by criss-crossing the country.
That is until he receives Livret C (
autorisation d'établissement) which will be earliest after 5 years of continued residency.
Fair question. Let's bring into perspective:
1. First of all, a teacher who earns 90k would be a bad teacher if he pays 20k in taxes. So, there is room.
Second, this teacher does not expect to live in Zug or Lugano in a prime location. He will be fine with standard housing in Winterthur or Oerlikon - not fancy at all.
Third, he will not want to hang out with people at
Ellermann's Hummerbar, the
Kaufleuten or
Café Odeon. A standard
Beiz will do, like it is o.k. for most locals.
Fourth, he will rely on 2. class train travel instead of a fancy car.
We can continue this endless. It all depends on the lifestyle.
2. On the other side (of the lifestyle) there is someone with paid in capital of 500k in a not yet registered company with a director, who wants to do business in a country he is about to explore. He starts with prime locations like Zug and Lugano. It can not be expected that this person has the same lifestyle than the teacher since he will -most likely- cater to an upmarket clientele and therefore he himself has completely different expenses than the teacher.
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As long as you know your way, have a down-to-earth lifestyle (small flat in working class district, no car, buy stuff at Migros and Denner, no fancy restaurants, daily commute by tram and bus, no taxi at all, no cinema, no theatre or Concert hall) life in Switzerland is affordable.
However, in this forum nobody wants this specific down-to-earth lifestyle.
That's what
@JohnnyDoe and me tried to explain -> Switzerland is prohibitively expensive when you want to live a life other than working class people do.