If after seeing your portfolio the client wants to offer you a job, he will get in touch with your representative to discuss all the details regarding your work. He may also need additional photo materials. Basically, the period from the first contact to signing the contract (or rejection) depends on the degree of the client's interest in you, the urgency to fill the position, and the level of professionalism in communication with you or your agency. Often agencies refuse to deal with a model or an agency if they give the impression of unprofessionals.