If you can get 30 pesos per hour, you will be doing well. Back in the old days ( early-mid 90's) when the currency was pegged to the dollar at 1 to 1, one could earn the equivalent of 20-25 US dollars per hour for private classes. Those days are long gone. I was able to live well working part-time and even save back then. Don't expect to live too well here teaching English unless you are willing to run yourself ragged.
Yep, I charge according to the individuals circumstances. However, I live outside the Capital, so the rates are generally lower - average 25 per hour - But it's not my main source of income, and I don't need it to live here.
I charge $45 per hour for classes in companies, $40 for private classes in my home and theirs for international exam preparation (IELTS, TOEFL, FCE etc) and $35 for conversation classes. Institutes are now paying staff $30 - $35 per hour for teachers - so students at institutes are being charged $50 per hour (more or less)
I have a couple of students on my waiting list. They have contacted me several times, but I just don't have space in my schedule to teach them right now. But they are keen to start. If any teachers are interested, send me a PM and I will send on their details for you to contact them and start teaching.