Costs ballpark £6-7K UK depending on who/where.
Another suggestion,
The Pilot Centre - Denham Aerodrome
Beware - a restricted FI needs to be supervised - so being 'freelance' (working for many schools) isn't always a good choice. Being freelance (one school calls you when they need you) isn't probably going to work too well at the moment either.
Earnings.....how long is a piece of string?