Going to build apartment complex, where to start?

[Brock Y.]

I own a good piece of land in St. Paul Minnesota just north of downtown off i94. Currently it has a SFH on it. The plan is to put an apartment complex on the property. It is already zoned for commerical so that is one less hurdle.

Questions:

1. I have never done new construction nor do I know how many units can fit on the land (I know St. Paul's guidelines for density). What costs can I assume just for feasibility of project? I would just like to get a few quotes on rough costs for a 2 story 20 unit building, just as an example. 

2. Where do I go to find builders, designers, architects? I am not local so I have googled and pulled a few names but assume there are a lot of national companies. Is there a good link to a directory of builders? Any one have one they recommend? 

3. If anyone has experience with cost of an apartment complex build I would be very appreciative. This project is 3 years away so I need to start saving :)