First impressions count a lot. Your portfolio is YOUR first impression. From those photos, clients guage how much experience you have, how much you're worth, and if you can handle the job. Welcome to the real world. However, any type of profession you want to get into takes money, time, and training.
Clients feel the same way about models.
Ten really great shots are much better than ten great shots and ten mediocre shots. Get a list of specific ideas you want to have shot before you ever contact a photographer. However, be cautious. Be sure to check out the photographer's work before agreeing to the shoot. Only one model was asked to come back for an interview.