6,000zl a month average
I'm on something similar after tax/zus- but also don't do much teaching at the moment - just a few companies that I've taught at for years. Plus a few private lessons for friends and their kids, for cash which isn't included in the 6000 - I don't charge much because I only do privates for people I know already. Translations are a useful extra, but some months I'm swamped with them and other months there are just a few. I have a few teachers who work for me; this makes up about a third of my taxable income - was more than that, and should be again soon :-)
I pay 1800 rent for a flat - it has three bedrooms and I sublet two to help with the rent and for company. Bills are quite low - just electricity gas and internet. Heating and water are on ryczałt and included in the rent. I don't live in centrum - that would be much more expensive for a flat this size, but here in Wola, I'm only 4 bus stops from Metro Ratusz, and walking distance to the Klif shopping centre.
Food - hard to say because I eat out a lot - shopping (including pet food) probably comes to about 1000, maybe a little less, but to my shame, I don't really keep track of it. Things like tea and coffee and non-foods etc, I buy at Makro on an invoice, since I can put these through the books.
I don't drive, so probably spend too much on taxis, but thankfully I can deduct some of these against tax.