It's on of those things that take a lot of time and patience. Unfortunately, when you snap a pic of a model, with intentions for a backdrop, lighting becomes a very big issue, and I for one am not that skilled of a photographer to accomplish this with any degree of success.
Also, in order to cut the model out of your pic fully and accurately takes a) a LOT of time, and b) some fairly expensive image editing software, which in itself takes a lot of skill to work with. Best would be if you have a photographer buddy who can snap pics of your models for you.