WIFI coverage in brick building

Hello, new to this forum and i'd like to see your opinion on this issue im facing with.

I have a project on a brick 3 stories apartment building and the owner wants to provide WIFI internet to all the residents for a flat fee per month. I know that brick and concrete are a big factor when it comes to frequencies.
One option i was thinking to wire each apartment and place a AP in each of them. Second option i was thinking, was to install high gain antennas on every floor at each entrance staircase in the building. One problem i'm facing with this is that the staircase is all brick wall.

Any opinion on this matter ?
Thank you.