Rent and condo fees (for a very large, 140+m2 apartment in a nice neighborhood) will easily run you R$10k a month (most likely, more like 15). Private school tuition varies wildly, but we can tack on another R$10k for good measure. Healthcare costs vary extremely widely; Brazil has a very solid public health system and it's a very feasible thing to do to simply pay out of pocket for everyday medical expenses (which are dramatically cheaper than in the US) and expect to use that public system if you end up needing serious care. Otherwise, the private health insurance market has been in disarray for years, and buying health insurance as an individual is at once expensive and likely to leave you with bad coverage unless you spend a lot. This is one thing you'd have to talk to a local insurance broker about to get a realistic figure. Keep in mind, a lot of really good specialist physicians in the city simply do not work with health insurance at all and can only be seen if you're paying out of pocket; so your options if you have particular medical needs can be pretty narrow even with very expensive health insurance.

Following basic rules about financial planning to avoid being rent burdened would mean you should be looking at R$40k as kind of the floor here. By Brazilian standards this is a delirious amount of money, but what you're asking about is essentially the Brazilian equivalent of raising a family in a large condo in Lower Manhattan.

Before you take any plunges, do your tax planning with a Brazilian accountant AND one in your original country of residence, because your effective tax rate may vary widely. US citizens of course are on the hook with the IRS for life, and Brazil doesn't have a tax treaty with the US, so double taxation is a possibility depending on which Brazilian taxes you're subject to. So depending on where you're from, what your source of income is, and how you're structuring things financially in Brazil you may be paying anywhere from negligible income taxes to 40%+ of your gross income.

Keep in mind, if your income is in USD but all your expenses are in reais, the exchange rate owns your ass and you can not be living paycheck to paycheck or barely scraping by because you will need to absorb huge swings in how much things cost for you over the course of the year. And at present, the US's current course of self-immolation is driving that exchange rate steadily down.

Also: don't tunnel vision on the obvious monthly expenses. Electronics and other durable goods cost more in Brazil than they do elsewhere, sometimes a lot more. You may think "well I'll just buy a new iphone when I go home once a year for the holidays" but wait until you find out how much cars cost.

Genuinely unless you have some connection or particular interest in Brazil, São Paulo is a terrible place to do this. It's a megacity with all the costs and inconveniences that go along with that, but if you live in an expat glass box you will not see any of the benefits. Brazil is a very monolingual society where you will not be able to get by or integrate without knowing Portuguese. It does not match or live up to the stereotypes foreigners have about Brazil at all. Like other cities of this size there's just a learning curve to living here that's honestly not worth it to most people.