I'm thinking about a bathroom renovation. The house is an attached
house, 18 feet wide. The toilet is on the second floor above the
kitchen.

My proposed renovation would really work out better if I could move
the toilet maybe a foot or so. I am planning on hiring someone
competent for this rather than attempting it myself, but I was
wondering if this is a really big job. I searched and found a few
posts mentioning moving a toilet two inches or so but a foot would
appear to be at the outer limit.