You will need to have a 100 hour inspection performed, assuming you do more than 100 hours between annuals. Flight instruction is flight "for compensation or hire".
Insurance may or may not be that expensive. I've done it, but that was in Alaska, where insurance is sorta obscenely expensive in any case. And, it was on floats.....to make matters worth. In any case, I would NEVER flight instruct without SOME insurance coverage, at the VERY least liability coverage. Are you REQUIRED to have insurance to instruct? No. But don't be stupid. If you have ANY assets, or ever hope to have any assets, these may ALL (including future salary) be subject to litigation if something bad were to happen.
If you think you can make money flight instructing in your own airplane, you are mistaken, unless you charge a FAIR price. Doing so for half the gas price and instructor charge? Great way to go broke fast. Why not just fly the damn thing where and when YOU want to fly?
THere's nothing wrong with giving flight instruction in your airplane, and charging a FAIR price for it. Get a quote on liability insurance (unless you can afford full coverage), assure the insurance carrier that there will be NO student solo in your airplane, and give flight instruction. You may be able to depreciate the value of the airplane, and at least the portion of flying you do in that airplane in flight instructing is deductable as a business expense.
Why try to do this on the cheap? Do it professionally, and you should have students. Figure out what YOUR expenses are going to be, figure in your insurance cost, your recurrency cost, etc, and then figure out what the airplane costs to fly per hour, based on your estimate of hours to fly in this venture. THat will tell you what you need to charge for the airplane.
As to what you charge for your own services as a CFI, I've been told by Rich Stowell that I'm nuts to flight instruct for $50 an hour....he says I should charge no less than $75. I never figured I'd get rich as a CFI.
MTV