Should my contractor be familiar with ADA requirements?

I’m remodeling a 4 unit apartment building I just purchased. How do I know what the ADA requirements are and if I need to comply? Is this something my contractor should know? Who is supposed to inform who in these situations?

The doorways needs to be 36" and toilet areas need to have a 36" turn radius, grab bars need to be in the shower and bathroom areas, at specific heights and reinforced in the walls. The contractor and the building owner need to work together.