how much should it cost to rewire a 1200 sq ft home?

It's gonna vary according to how old the existing electrical components and conduits are. Also depends on building materials on interior. (Plaster, Sheetrock, Paneling...). There's a basic pricing model online, but I doubt you will get an accurate quote. Just have a local hatchet-head come out and give you an estimate. Most of them are free, especially if within a few miles of your residence.