I am both
I spent two years instructing before that illusive first job came along. I was lucky that the airline i work for likes people with an FI background.
The good things are that it will vastly improve your hand flying skills, general knowledge and confidence. If you can, branch out to night, IMC and/or CPL instructing.
The poor side is the cost of training and the poor salary.
I have been on the RHS for 8 months now and am now going back to instruct on my days off. For two reasons. One, a bit of beer money and two, I found it really good fun to fly a PA28 etc.
Also, the FI market is not in a good way at the moment. People leaving to join the airlines have left a gap in the once abundance of availaible FI's. So don't go out there and work for a poxy £15ph with no retainer. I know that recently CTC and Qatar Aero Coll. were looking for CPL instructors and the pay was OK.
A friend of mine earns a good wage as a ME/IR instructor.
This may be a bit far down the line but there are options if you were waiting, like me, for a FO position.
Good luck.