Guesstimates on the cost of an enclosed porch?

Hi, I have to start budgeting to have an enclosed porch put on the back of my house,a single story ranch type. It will be a straightforward building,12x16 constructed on top of a platform much like a deck (to be constructed), standard framing, metal shed type roof. Four vinyl windows, plus sliding doors.The interior would be finished by us to cut costs. I know I will need estimates from professionals as costs vary widely.But I just need a VERY rough idea of what it might cost. Located in the Hudson Valley NY. Thanks