RB
Sorry, don't necessarily agree. If the co-pilot is the right sort of person who can LISTEN AND LEARN, they will turn into a great captain one day. That is to say if the captain he/she is flying with gives them opportunites to learn and not just keep the seat warm.
I have flown two-pilot ops with many a young/inexperienced co-pilot and have found that if you constantly keep them on their toes during a flight, they will appreciate it. I have certainly been taught a thing or two by them.
On the original question - I reckon $300 / 300GBP per day is a good casual rate. Salary - don't know ($35000 per year ????)