Going rate for private English lessons

Between 15€ and 80€ an hour?

I guess that depends on what you offer.

Qualified, experienced teachers would expect rather more than a University student etc. Are you traveling to peoples house/offices or doing it from home? Do you have specialisms like business, legal or medical?

Are you going to do it officially or in the black?

It's a competitive market as well.

You could pose as a prospective student and call up various tutors.

As you can see, it is difficult to say.

Who are your target audience? What can they actually afford? Kids, individual adults, groups, businesses?

You have to decide what you are worth and see if the market agrees. You'll find out very quickly if it is too much or even too little.

Absolutely agree with last response. I teach English. 20 euros for conversational sessions ( 1 hour) / 40 Euros for 1:1 lessons including assessment/ written work/ homework etc. The more preparation required, the more expensive the lesson. Oh and I have thirty years qualified teacher experience and not just a TEfL cert.