Do not forget that you do not HAVE to work at any of those places. You can hang your own shingle and make your own business. Visit a few local airports, write down the tailnumbers of the based aircraft. Stop into the FBO's at those fields and see if they're looking for CFI's... also make note of the rate they charge. Use the FAA registry database and send all the based owners a postcard offering a good rate on their BFR's, and IPC's... knock 5 bucks off whatever the FBO was charging for their CFI's.
If you want to really get fancy, cross reference the owners with the license database.... you may find yourself a few owners who have bought planes to learn in rather than renting... it is much cheaper to do it that way (at least in the northeast) and is much more common than folks think...
put a free advertisement in the classified section of AOPA, Barnstormers and anywhere else you can list it... even Gliem now has a free CFI list online.
Sign up for the FAA safety seminar notification list and start going to the seminars... meet the FSDO folks and offer to help set up and such... do it a few times and become a regular... they will eventually think of you when they start looking for Air Safety Volunteers.... which looks nice on your resume, and on your business cards... you will get referal work from the FSDO that way as well.
It is slow to start, but I know several people who make a nice living teaching and do NOT work for FBO's. Write a few articles for Atlantic Flyer or your regional aviation rag... become a regular contributor... you would be surprised how quickly your name can get known by alot of people.
Eventually, you can be able to pick and choose who you will teach, and what you will charge... another friend of mine gets $1,000 per day mentoring/teaching TBM700/850, Baron and Bonanza. He works about 5 days a month in an airplane. He also travels all over the US to do it, but his expenses are paid by the folks he's teaching. In spite of what you see in the typical FBO's, there are plenty of people willing to pay top dollar for a professional teacher. He pretty much has it made... The rest of the time he is at home writing editorials, marketing himself, attending simcom a few times each year (for each type)... he's basically retired having fun.
places like
www.vistaprint.com will make business cards for you for free (their ad is on the back in small print) and do postcards really cheap too....