I worked full time as an instructor 2001-2003 and had to make myself available 7 days a week in order to average 600 hours annually. That makes for a lot of drinking tea between students or waiting on the weather.
Whilst not thinking about the financial implications I enjoyed every minute of it and would not turn the clock back. However as I only earnt when I flew (block to block) even a £10,000 salary would have been manna from heaven!!!!! Things were just getting desperate when the first commercial job came along. 12 months on I can look back with fond memories but I know the reality was far less romantic.
If you are serious about making a career from instructing then aim high and find a position with one of the bigger commercial schools where a salary is paid. Otherwise the advice about instructing on the weekend or after the day job should be given serious consideration.
Best of Luck...............