The area circled is two levels of roof, on top of one level of roof that I assume he wants raised up to the level of the home behind it?
Hard to really understand the scope of work based on one pic and a brief paragraph or two, but that isn't an easy project. You have; demolition, temporary weather protection, complete re-frame, HVAC, electrical, interior finishes, roofing, siding, insulation, soffit, gutters, etc.
And .... you need to make it all blend in so it doesn't look like an addition which may mean re-roofing and painting or siding the balance of the home?
Best idea would be to call a reputable remodeling contractor and tell him don't put too much time or effort in it, but give you a ballpark budget price.
If the ballpark number doesn't knock you off your feet, move ahead with design and firm pricing.