I estimate the basic rehab to modernize it at around $15k, but more likely $20k-$25k to get it to the higher end of the local rental market. 

I projected 5k for each unit to modernize/rehab and wouldn't be willing to accommodate additional expenses.

Once I got over the traditional thinking process that many of us grew up with and embraced the modern REI mindset of leverage and equity growth, I was able to pursue REI.

This is more of an art than a science but good luck and you'll figure it out.  

It's a 700-page novel written in 1943 mostly exploring Modernism in skyscraper architecture and selfishness in art...yeah, it stuck out there between the half-inch-thick self-help and business books.

It's not rocket science. 

Additionally, not all mansard roofs are "flat" on-top, traditionally many/most mansard buildings have a low-pitch hip top.If your building is a true mansard roof (and not the modern "hat" sitting on the top of a building), it would be big job to rid yourself of the mansard.

I'm curious if that's an indication of a soft market, or a market that's not as modern? 

Marc's is modern and he' ready to back it up with as much consultation as you need. 

It's part art and lots of science (especially measuring results and acting on the measurements.)