There are youngsters who are so used to consuming free content on the internet that they sometimes extend that to things that obviously aren't for free. They are all in for a rude shock when they get their first brush with real life. As they say, there is no such thing as a free lunch in the universe. <em>None</em>.
It is in fact rude and remarkably foolish to expect a <em>teacher</em> to teach for free, just as it is to expect a lawyer to give free legal counsel, a doctor to treat patients free of charge or the supermarket to give away free groceries. That's charity, and applies only to those who have nothing of value to give in return. Even as a young student, I never expected charity.
The traditional <em>gurukul</em> system of education in ancient India looks like the ultimate free system, but in fact was nothing of the sort. In brief, it had young boys to go to a sage's hermitage, stay in residence for several years and learn, for no apparent charge.
To put that in perspective, those were the days of barter economy when money wasn't yet a thing. The youngsters were in fact the unpaid workers at the hermitage who did everything from taking care of the hermit's cattle, tending to his vegetable patches and crops, fetching water, cleaning up the place and even massaging his legs and feet.
To that, one may add that even this was not universally accessible. Only those born as brahmin boys were entitled to education. Girls and other communities were not worthy of receiving education.
I don't correct long texts full of spelling and gramatical errors, often so bad that one is left wondering what it means in the first place. I would only respond to something if it can be done reasonably briefly and it's something interesting. If I need lessons, I shall certainly pay for them. Having an exchange partner is a good secondary strategy, but no substitute for a teacher.