1. A truly interested agent will never ask you for money.
They will never suggest to you that you need to spend money to make money. If an agent sees real potential in you that is where they will make their money, by taking a reasonable cut of the work that they get for you (usually no more than 15%). Legitimate modeling agencies do not have handling fees, signing fees, agency fees (outside of their cut of work done as noted above) or any other kind of up front before-you-can-be-signed fee.
2. A legitimate modeling agency will never ask you to pay up front for your own test shots or pay to build your own portfolio.
They will invest in you and make their money back when they get you working. They will arrange for your test shots and only expect you to show up at the shoot on time and with a positive attitude. Most agencies have agreements with photographers and make up artists whom they pay to take their test shots and even build a working portfolio for an up-and-coming model. Models do need portfolios but when an agency is really interested in a girl and thinks she can make it as a model they will not ask for any money to help build it.
3. Another thing that models legitimately need but should never be expected to pay for is a comp card.
A comp card is the models equivalent of a business card. It is usually about the size of a 4x6 photograph, has between 3 and 5 shots of a model with different looks and includes a brief bio that includes basic info like eye color, hair color, height, weight, age, and shoe size. Some aspiring models do pay for these themselves but these are girls who are looking to be signed, not models with an offer on the table. An agency that wants to develop and represent you will never ask you to pay for your own comp card or for the pictures necessary to make one. Also, along these same lines a legitimate modeling agency will not ask you to pay to set up a web profile or other online promotion tool.
4. Becoming a model should not cost you any money up front, even for things that sound legit like professional modeling lessons.
This can not be stressed enough. An agency that is truly interested in developing you as a model will not ask you to lay out any money up front. They will be looking to make money off of you in the future and will be willing to make an initial investment in making that happen. Modeling is a business and businesses mean taking risks, a legitimate agency that thinks you can work as a model will take a risk on you. This means that they will never ask you to pay for modeling classes of any kind. They may ask you to take some classes, especially runway or posing classes, but they will never ask you to pay a penny to do so.
5. Finally, but very importantly, no legitimate modeling agency or agent will ask you to take nude or suggestive photographs, no matter how tasteful the presentation.
Photographs like this are usually highly artistic and require a certain degree of experience on the part of the model to make them work. Legitimate modeling agencies will not ask an inexperienced model who likely has lots to learn about their best angles and how to pose to take risqué photos. What they may ask is for you to take a picture in a bikini or even lingerie but these shots will be catalogue-looking, soft, somewhat innocent and not overly provocative. If an agent asks you to take a too sexy picture right away walk out the door and dont look back.