A CRI does not come out of the box restricted for a start so has larger opportunity for freelance.
If a school needs an Instructor and they have work for a CRI then who would you be irritating?
Personally I would suggest that you think outside the box. Aviation is a much bigger place than the average flying school and there are far more fish to fry for a freelance!! If you want to teach for the PPL you will need a school or a club. You will need an FI to teach for the PPL.
However I know of quite a number of schools who use part time CRI's for club checks, recurrent training etc. Also if you do the GRI you will find yourself with plenty of work, in my experience most of the hours building FI's are not interested in teaching Ground School as it puts nothing in the logbook.