Is it OK to charge money to give a concert?
That question does not apply within the UK - you will never have the opportunity to be paid for a concert except in extreme circumstances. Music in Britain is not considered a professional activity, therefore no-one expects to pay you.
However, I'm talking to you - out there, all over the world (wherever there's a computer, anyway...this is not actually everywhere, you might be surprised to hear).
I would really do concerts for no money. You're paying me by letting me play - that's one of the things that keeps me alive. However - I do need some money to literally physically survive long enough to do the next performance. And I'm quite cheap!
For a free concert you'd have to put up with my own choice of repertoire. I would take requests (where possible) because I'd be doing it for you, for the audience, so I'd like to give you what makes you happy. It's called GIVING a concert, not taking one away!
But what you like isn't always what's good for you. Lots of music has been forgotten or hidden so you will need to hear some of that. Pleasing the audience has a variety of meanings with me.
Please give generously! I will try to do the same.