1. What you need is an example, so look at some fashion/blogshop photos and settle on a style you want to emulate. No use trying to tell the photographer you want a "light airy style" but end up having different ideas about it. Choose a talent who you feel best at carrying out this style, clothing apparel brands are usually quite insistent on what kind of talent is modelling their clothes, if you have a preference then you need to sit down and consider it. And to the photographer, show right away this is the style you want. Those who have no confidence in producing it will not come bother you. Of course if you're the kind anything goes then lucky you, every photographer will be climbing over each other offering their services.
2. If you want the talent to just stand there and produce 3 standard poses then maybe you don't have to pay much. If you want something a little different then expect to pay more for experience. Check out
model mayhem. Payment is usually per hr. Depending on number of clothes, how experienced the talent and photographer and how demanding you are, better to over estimate the amount of time required. Changing of clothes, equipment setup, toilet/meal breaks, ironing/steaming, minor wardrobe malfunctions, equipment malfunctions, styling, all this eats into time.
If shooting in a studio then factor in studio rental costs. Even if it's owned by the photographer please don't expect him/her to eat that utilities bill. Charges are either by hr or items. Other chargers are transport/meals, DI & equipment. This is heavily dependent on the quality outcome you chose. Makes sense that if you want a very simple standard kind of style that is easy to shoot, certain costs like equipment, DI may be less. If you have an elaborate demanding quality of photos then the photographer has to charge accordingly for time & equipment spent.
3. MM for talent & our Services Wanted in Marketplace for photographers.
State the style you want and consider which photographer to use. Ideally his/her portfolio should contain images similar to the style you want, or at least capable of convincing you he/she is able to replicate that style. You don't want someone blundering through the shoot, because firstly if you're clueless and the photographer is only waiting for your cues, it is just a waste of your time & money. You might end up settling for something you were not intent on getting, or that you went over budget because the shoot could not finish in projected time. Unless you have a strong sense of what you want, better to have the photographer take charge and you can learn along the way. However make sure the photographer does not go haywire nor overrun the time and then again you have the same problems. The better photographers always have their eye on time, some newbies may get too excited and lose track. One of you has to be the time-keeper. You are running a business first, having fun is secondary or if it is FOC.
Mannequins are not free, and while hangers are, they are also shapeless. Talent hire = renting/buying a mannequin = more time per item because the hangers fail to bring out the best quality of apparel. There are pros and cons to using each, best to discuss with the photographer. Again if the photographer has no clue or opinion, then good luck to you. As a new business what doesn't hurt is more contacts, you may save some money from hiring a talent, but you definitely lose that opportunity to gain an audience. Think about it.