Don't give up your day job!
By all means go ahead and do your instructor rating. Find a school where you feel comfortable, and where you would be proud to bring friends who wanted to have some flying lessons with you. Take any "guarantees" with a very large pinch of salt. Ask if you would be able to do some part-time/casual work once qualified through their school.
Then, do the course and keep up the day job, keep those business skills current, and see if you can do a little bit of instructing work in your spare time.
Otherwise you could find yourself in the situation Jarse described, and feeling very bitter about it all.
If you are out in the big wide world you have the best of both worlds, earning a decent income, doing a bit of flying in your spare time, gradually building up your experience. As Dep said, there is no short cut. The only way ahead is to build up a good reputation and a big network of people in the industry. Then one day the time will come when you realise that you CAN give up the day job. In my case that took eight years. Be patient!
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