I am interested in purchasing a home that has low ceilings on the second floor- about 7 feet. It is a basic colonial 1 peak roof. Is it feasible to replace the roof and rafters and raise the walls at that time?

Can you and would you are distinct questions.

Cost is a factor and you may need additional permits if you block any sight lines from neighbors houses if you are on a hill or near a lake.

That said an architect or engineer should definitely be brought in to access the weight additions to your existing frame etc as you ill be increasing the load.

I am buying a house that has a low pitch. Can this be raised to a higher pitch? Do I need to set in new rafters or just build up over the old roof? Will it be stable in a wind storm?