There is something I call the «broad shoulder» which is a set of a few thousand authors who are all selling tens of thousands of units per year. (advancedfictionwriting.com)
I usually estimate between $ 400 and $ 600 per unit per year in maintenance on a multifamily and am not too far off most of the time. (biggerpockets.com)
You as a buyer may budget $ 700 per unit per year. (remonline.com)