How much will I make?
YOU: "I don't know. What you make is ultimately up to you. I don't know you well enough to know if you will make a dime. You may go on to huge success or you may not make a dime. There is risk in every business. There is considerably less risk and this business then and any other business when you consider the minimal investment to start your own million dollar company in league with a very successful company with a very popular product. What we are offering isn't a guarantee, it's an opportunity. If you're looking for a "sure thing", then your not cut out to be an entrepreneur in any network marketing company. All businesses have risk attached. "

Tell them that. Note that practically everyone else they have talked to has probably told them they will make a fortune and it is all very easy. People respect honesty, so be honest.
Bob