Depending on your area (yes NYC, charge it high), there are several factors to consider, which many here have covered. I'd say get a certification as soon as possible, while then you can also continue teaching.
As melismatic said, don't charge too low, or people won't take you seriously, and just goof off. As a new teacher, however, you should charge at slightly-below average prices. Despite what you think you might be good with people, it's just a secondary measure to make sure, and besides, you are doing this for experience.
After a few months (a year?), you can increase your fees. If you have lots of students (which is a very good thing) then you can raise it even quicker and higher. You can raise it to your desired price or continue building up, so as not to lose a few customers along the raises.
Whether you want to go to student's homes or student's coming to your home is another thing to consider. It's basically competing between the time for travel (therefore less students, and you get more tired, and you won't be in top condition) + traveling fees (gas) and the wear and tear of your piano (particularly if you have advanced students playing Bartok ruthlessly on your piano).
Also, for some reason, there are people who go to teachers who charge obscene rates ($500 USD a month?). There seems to be no top limit you can set, but just make sure you can justify it with 30 years of teaching experience, with your plethora of certifications.
Speaking of which, I should start teaching piano, and of which, I shall hijack this thread.
How do you get students?