Hi Mary!To answer your questions...
a. As you know there are venues (coffeehouses, societies, etc.) that hire people to make music. When you audition (live or via demo tape) these people will decide whether you are good enough in their particular venue to sing for your supper.
b. People should be entertained and leave the venue uplifted.
c. I refer to a. above. Try too to develop a unique repetoire of your own largely exclusive of recorded folk singers.
All the best,
Dan