If you are interested in modeling, I have to be blunt with you and say that, unless you have been told to create a book, or are already a model and simply need to diversify your book, that you think twice about paying me or any other photographer to take your pictures.  The reason I do not recommend paying for professional pictures (if you can get them for free, that's another story) is that all modeling agencies will be developing their models exactly how they want.  It does not take a flashy portfolio to get into an agency, especially for younger models.  Nowadays, all one has to do is submit polaroids of facial profiles, full body shots and simple close-ups to grab a modeling agencies attention.  My personal experience is that they will be taking rough polaroids of you anyways to get a more accurate representation of what you look like.  It is actually more in your favor to submit pictures that truthfully show your features without heavy makeup and soft, unrevealing lighting in order for an agency to see your full potential.

If there is interest from the agency, it will put their own money and time into testing you with their own photographers and developing a book/portfolio they can then show to their clients.

It should be noted that the career of a model (females especially) is very short.  If you are in your twenties and do not have experience yet, you may want to get professional pictures done for something more to show for.  However, please only consider this after you have made a good attempt at getting into the modeling industry without having to pay someone hundreds or even thousands of dollars - someone who says just the opposite of what I am saying now. 

If you would like to diversify your book or develop a book for either high fashion (meaning you must be at least 5'8" tall) or print work (no height requirements) there are some good photographers out there who can help you out.  Just be sure you do some shopping around.

Also, remember that most modeling agencies have petite and plus-size divisions.  Don't rule yourself out because you are not ideal for runway and high fashion.  And definitely don't pay someone large amounts of money who says they will make you a star.

If you are truly serious about modeling, you will need a comp card.  Whether this is done through your agency (most likely), or not, a comp card is the same thing for a model as a headshot is to an actor.