What is the cost of living in Brazil - Rio

This is more a list of comments than a proper answer.

I don't know Volta Redonda but Rio is a very expensive town (for Brazil standarts)

Credit Cards

Locals use it more than cash for day-to-day expenses meaning you also can use it to cover almost anything (make a call to be sure your it ill be valid overseas). Also it ill take the Real x Dollar exchange rate of the day of you pay you credit card bill, meaning you ill be gaining a few dollar unless a very unexpected Real rise happens in next quarter.

Food

Eating out means you will rely on inexpensive restaurants and fast food. Here you ill find a lot of of Self-services and Prato Feito In self services you (in general) pay per Kg and Prato Feito you receive a already filled dish. In general Prato Feito is cheaper/Kg but you, like me, eat a lot less than a pound/lunch you can try a self service per Kg.

For fast food there are some franchises you maybe are familiar like Subway, Mc Donalds, Burger King. But these are never the cheaper option. ;)

For dinner you can try some fast food & pizza delivery as usual.

Finnaly note using inexpensive options means you are unlikely to find someone can communicate in english. A good idea for start is to try to hangout with locals if you got the opportunity. They for sure ill know the better options in town and can help explaining things and with communication.

Health & Hygiene

If you need some medicine bring it with you. First you don't know how much it's priced here second don't expect any drugstore to sel you anything without a prescription in portuguese (sounds obvious but I already witnessed a angry tourist mother trying to buy a prescribed medicine for a kid).

Drugstores in Volta Redonda

Soap sound inexpensive but sum up all that little toilet things you ill use and you see how much that can cost you. Bring at least the first week supply while you try to adapt.

Laundry Can be a concern if you cannot use a washing machine in your place you ill need to find someone to do it for you. In general paying someone to do it is a lot cheaper than using laundry shops but you ill need local help to find someone.

Eletronics, Footwear and Booze That's where you can make some profit and use it to pay your expenses. Due to taxation and other peculirities some stuff can be a lot more valuable here. You can try to bring a brand new iPhone, Nike, Reebok, Johnnie Walker.

Miscellaneous stuff Don't forget there's always unexpected expenses in a 12 weeks trip. You can become inclined to buy some souvenir for you and friends. Locals also can try to give you the best and take to a Churrascaria or you can get used to hangout with new friends and need a third budget for the beer.

I posted some google searchs (terms in portuguese like farmácia, drogaria ~ drugstore) If you get any question about any specific term you can try out this other SE site

From this article from 2012:

The [Brazilian state] defines those in the middle class as people who live in households with a per capita monthly income of between R$291 (US$145) and R$1,019 (US$500) and have a low probability of becoming poor in the near future.

Today, those dollar amounts are closer to double the reais mentioned in the quote above, so, somewhat depending on whether your estimate includes accommodation or not, you should be able to live in similar fashion to some people in Brazil's middle class.

However, as an expat, you're very likely to spend more, sometimes much more, on pretty much everything. If you're happy to eat at lanchonettes (snack bars), you'd be able to get away with 20 Reais for a meal, but if you want to sit down in a 'nice' restaurant, the cost could easily be 50 to 100 reais, not even necessarily including drinks.

I don't know Volta Redonda, but I do know Rio. I currently live there half the time. Living off 200 reais per week in Rio, as an expat, would be tough, but possible, assuming your accommodation is paid. But very, very tough if you intend to mostly eat out.