There are jobs you should take on and there are jobs that you should not. This is a poor choice of material for this application and clearly a low budget job.
Be honest with yourself. Why do these people want to bring in a completely inexperienced person to do a job that involves fixing something that they did or had done very poorly? Who would recycle material that is inappropriate to protect the erosion of a paved driveway? (an idiot or an extremely frugal person or someone looking to take advantage of someone who does not know what he is getting into or most likely all three)
If you try to fix this, you run the risk of being responsible for everything to do with that erosion and that driveway to which there is nothing on this site that would make me think it was built well.
If you do some searches on this or other similar websites using the key words "pre-qualify" and separate searches using the key words "red flag" it might become clearer.