Could also just do a really decent quality mesh to go from the basement to the 2nd floor. There are a lot of systems that will cover that distance especially as a temp fix until the lines get run.

They wouldn't be able to do MoCa as the lines to the apartment have been cut so there is no Coax, it is a great suggestion though. This would work if they have any active outlets in the apartment, but so would just moving the modem.