It is possible that an 18-year-old model makes more money on a job than a 16-year-old model. However, each job and client pay a different fee depending on the type of shoot, the time required to shoot, the experience of the model or whether the model has agency representation.
Regardless of age, a model that has agency representation is usually paid a fee that is determined in a negotiation between the client and the agency. Agents have the ability to set terms for each job and usually set a pay rate based on the work the model has done or how high the demand for a model is. Once the terms are negotiated, the model makes a choice to accept the job or not.
Freelance models have a bigger challenge to face, especially new or younger models, and often face lower rates as they build their portfolios. They can increase their pay rates by being as professional as possible and skilfully delivering photos or runway performances. The more experience a young or new model attains, the more she can charge either per hour or per day. A few things a model should consider when determining a fee to charge a client are the client's budget, the type of job they are seeking, the length of the job, what if any perks are included and what the model must provide to make the job happen. Freelance models of all ages have to be flexible and charge on a case-by-case basis.