Solar panels, combining comed account

HI!  We own a six unit building in Chicago IL and we are looking into consolidating all to just one electrical account, and installing solar panels.  We would like to meter electrical use for each unit and for the building and remain on grid with Comed with one account.  I'm not sure this is possible.  I have many questions maybe someone could help me with.  

First is it likely that a flat roof on a six unit building that also has two double garages, be large and strong enough to hold the solar panels?

Secondly I'm sure there would be electrical work involved to move from 7 comed account to one, (and also for some units to use electrical service in garage for electric cars).  How costly and realistic is this?

Third, we are researching purchasing the solar panels independently of the installer/electrician(s).  Do anyone do this type of work?

Forth, in regards to incentives:

A There is a federal incentive that will credit back about 26% of the cost of panels and installation in 2020. Credit is not refundable. If we installed the panels and a building, our condo does not have tax liability.  As such, does anyone have experience denovo-ing this credit back to the unit owners?

B.  Does anyone know about RECS in Illinois and if it would apply here?

C.  Net metering with comed posses a problem because they use the average of 12 month's electrical service for the basis of the amount of electricity they will buy.  This is an issue because I want to combine all electricity into the building account, the smallest amount used but makes the most sense.  Does anyone have experience negotiating with comed on net metering?

Thanks for any help you can give me!

Kathy.