When working with a freelancer, as long as you have work for them to do, and the pay comes along with the work, than the freelance photographer will stay engaged and continue to work with you. Be sure to include them in your plans for photo shoots, ask them if they would like to use different shots for their portfolio and just work together. You are both are in the fashion/art industry and it is important to work together as partners in a job that helps you both succeed. Take the time to find a freelancer that is on the same page as you, understand what you are trying to achieve and one that you can keep the communication open with.