Back up plans is another way of saying "Get a real job"
If you have no other skill sets or training (college or Uni for example) then consider things like working for McDonalds/B&Q or contract labour/driving/office admin work. That sort of job will generally be fleixble enough where you can leave fairly quickly without much or any notice.
Don't forget, unless you are very lucky or rich, you will be finishing training and likely to be saddled with some form of loan that will need servicing.
The chances of getting flying work straight after training are not likely to be good, so it is best to plan for the worst and hope for the best.