I was looking into buying a painting, and also thinking about how to have it framed for hanging. One option that I discovered is this idea of a gallery wrap.
What this means, quite simply, is that you dont need to buy an ornamental frame to put on after the canvas is stretched. This makes the whole process cheaper, and when you order the painting you just ask for a gallery wrap finish.
This means that the painting is prepared with an extra 10 cms or so of painted border, with the colors of the oil painting reproduction extended out round the sides. When the framer stretches the canvas on to the wooden stretcher, there is no unpainted white canvas to see on the edges, next to the wall that the painting is hung on.
This makes the painting look better when its hanging, and its a good idea. Of course, you dont need this if you plan to put on a decorative frame, because the frame covers the blank canvas on the sides of the stretcher, but its a neat idea if you have a more contemporary painting, like a Leger or a Kandinsky that look better hung like this.