Question about the feasibility of enclosing a mobile home with metal frame?

I've been considering cost ideas with a new home. I've been thinking about using a mobile home as a starting point so I can live in it as I build around it. What are the pros and cons of doing this because I want to widen it as I go, so I thought about enclosing it with a metal frame and metal on the outside. I've seen homes where people have converted shop buildings and it turned out quite nice looking.