First off, +/-$50K per unit. Depends on your contractor, connections, experience, etc. Also I typically recommend clients add the rehab cost of at least one unit onto the project to cover general building improvements. Tuckpointing, roof, porch, whatever the items may be. I do cost estimates regularly, so when I go through a building the numbers work.
Ok, now you aren't going to like the rest of this answer but try not to hate me for it. Are you insane? Have you looked at how many unsold condos there are on the northwest side, have you looked into how hard it is to get financing for a buyer on a new condo building, do you have a niche - is there a reason someone should buy your condo instead of one of the many already built, do you have experience? If this is vintage brick you have a marketing advantage over CMU if you know how to use it.
I realize if you own a brick shell you obviously need to do something with it. I have to tell you though I would recommend thinking long and hard condos. I seriously doubt Condo sales will be any better in the fall of 2012, your likely sale time.
Rental may not work for you from a finance standpoint, over the next few years it may be a better option though. Depending on variables you could apply for money with Community Investment Corporation, no I don't work for them.
Feel free to give me a call or drop a line.