How do you familiarize yourself with your buildings?

x-post from r/PropertyManagement - Looking for advice as a newer property manager/operator of commercial buildings: When you take on a building, what processes do you use to learn and document the various systems and maintenance records for your buildings? I'm working with a family member who has been servicing our buildings for 30+ years and has everything more or less committed to memory, and he's asked me to make 'manuals' for each of the buildings. Does anyone else out there keep a manual or other document for each building? How do you organize them? Which features would make it into such a book (rent, utility accounts, furnace model, etc)? Thanks for any input!