Working on a school assignment and I'd like credible and actual numbers for future references when I decide to buy a building for my business.
Unfortunately this isn't the kind of information we specialize in. I can suggest reaching out to an architectual or project management type firm and see if they'll help you, a lot of people like to "give back" and share experience and education, so I would think they'd like to help you with your assignment.
Best of luck!!