Modify a picture with photo realstic edits

We need to show a client what a home would look like with a porch added. I have a few pictures of the exterior of the building, and need it edited to add a porch to the front of the structure. It MUST be photo realistic editing. and it MUST depict an extension of the original building, with original looking materials, finishes and textures. You can most likely cut, edit and paste portions of the existing finishes to complete the work... will provide a sketch of what is needed, the original pictures, and some notes and will be available to give input on the outcome.