Traveldude is correct.
I was a private tutor and made between 15-20 bucks an hour and usually worked at least 20-30 hours a week. Mostly corporate gigs. That did not mean I could count on 900-1250 a month. I usually made about a grand a month, but some months, like December or July whith lots of down time, I could make as little as $5-600, but still enough to get by.
I did not have a TEFL nor a teaching degree, but I was able to quickly build a good client base simply off referrals.
The one trick I did to make sure I kept my students paying was to offer a 10% discount if they pre-paid a month in advance. With that, I had a very strict cancellation policy. If they cancelled past a certain hour, they would loose the class. If they cancelled more than 3 times in a month, they would loose a class. At first they did not like my strictness, so I added a counter part, if I cancelled past the same hour, they would get 1 class for free or if I cancelled more than 3 times in a month, they would get 1 class free. in 2 years, I did give 2 free classes, but the result was the students respected my policy much more because it respected their time as much as i requested respect for mine.
The other issue is you needed to be a good teacher where the student had a good time and felt like he or she was learning. If not, they will cut you pretty quick. They will not tell you as such usually, they will either start cancelling classes or tell you something came up and they will not be able to continue. If that happens to you often, you should question your teaching approach.
Teaching materials are easy to score. You can buy them all over town (new, used or pirated), many can be downloaded off the internet and from time to time you see them advertised for sale here or other expat websites for teachers leaving Peru or leaving the profession. I recently sold most of my old materials in such a manor.