Build a Website of Photo & Retouching

Hello everyone, I want to build an interactive website for photographers (just me for the start) and retouchers. The basic idea is that a photographer can post some pictures that need retouching and the retouchers post their offers and the photographer chooses who to work with. So there will be two types of accounts: photographer and retoucher. Each one will also have a link to their portfolio/work. The part with the interaction is where the photographer will post the pictures that need to be retouched, setting a price range and the retouchers will apply, naming their price. The photographer will pay in advance and the money will be unblocked for the retoucher when the photographer received the pictures and is everything ok. At this part I am open to ideas. Two more things that I am interested here about: 1. There should be a copyright mask over the retouched pictures that the photographer sees, so there is no way he could copy them and ask to refund. 2. One of the most important things is to have a Before-After gallery with zoom function. So you have the two images - the before and the after, which are both at the same resolution - and you can zoom in (for example with mouse wheel) and then see the "Before" part in that zoomed area by pressing a button (right mouse click or spacebar). What matters is to be able to zoom in and switch between before - after. (No need of that vertical drag line, just instant switch between the before and after, no other effects). This type of photo gallery is mandatory for this project. I attached an example of before-after images with the same resolution size. As you can see, they are pretty big and you can barely see the difference of the leg for example in "fit screen" mode, unless you zoom in and then switch to before, having the whole leg in the screen. If you need more information about this, please let me know. Best regards, Bogdan