sort of what Brett is implying with the "where i work" comment is that location is also a key factor in pay.
at the flight school 5 miles from where he is - their pay may be as much as 5 or 10 dollars different from his.
Scenario A: will you be working for an accredited flight school with a contract and a hand full of other instructors with many students and enough planes to go around?
Scenario B: will you be working for a college with a flying program?
Scenario C: will you be the local independent flight instructor at a small town air field?
the pay scale is pretty universal - at lease here in the USA - i have seen as low as 15 an hour to as much as 50. when i was doing it i started out at 25 an hour and went up to 30 an hour when i started offering multi and instrument training.
of course how much your being paid per hour means nothing unless you start putting hours into the hat.
Each of the above scenarios offers different advantages and disadvantages. CFIs who work with a school or college often only get the schedules and the students that the school is willing to give them in return they get more money and more flight time. but independent CFIs working for themselves usually make their own schedules and THEY decide when they will get vacation or days off etc.
My advice - get a cheap apartment- er... FLAT, and a room mate who knows well enough to turn the lights off when he leaves the room

or - marry a nice pretty woman doctor.