the cell carriers will give you a trial period. I have found that Verizon's data actually has better coverage than voice, in many places.

If you put an AT&T or Verizon MiFi on the 3rd floor or attic you'd be able to connect up to 5 computers on the lower floors concurrently, with your own private hot-spot, and run at broadband speeds. You get 10GB per month before you get hit for extra charges. More than enough for web and email, but not enough if you watch several streaming movies with Netflix etc. Even if you watch movies and go over, it may be worth it for the entertainment value, at times.