This weeks 99% Invisible podcast is on this exact topic. The bottom line is that while it is technically possible, it is really expensive and only makes financ

This weeks 99% Invisible podcast is on this exact topic. The bottom line is that while it is technically possible, it is really expensive and only makes financial sense if you create luxury apartments that can charge the very highest levels of rent. Also the legal and regulation red tape is a massive problem making many projects impossible to do, even if on paper they might be viable. In most cases the most practical solution, after taking financial and regulatory considerations into account, is simply to leave the building empty and hope for a future upswing in commercial real estate.