A certain mystery surrounds the modeling industry. There is no clear cut answer to that question. Because of this mystery and uncertainty, a great deal of room exists in which a scam artist can work. Since a modeling agency is often the key to becoming a successful model, this is where many scams take place. There is no easy answer.
Most agencies are small, independent businesses working in a very competitive market place.
These seem to be in constant flux with new ones starting, old ones merging, and some closing up shop. This makes it a real challenge to find just a legitimate agency, let alone a good agency. Remember, a modeling agency wants to be easy to find so a phone listing is a must. From the agencies' listings you may find they are often, also, modeling schools. If there are no agencies listed for your area, you may have to check with the closest large city.