Estimate a/o average sq ft bld cost for a small t'home community

Greetings forum,

I'm reviewing a possible,  "smallish" - 26 units, townhome development for a client.  The land is about 90% developed with major utilities in place including sewer, and most concrete in place in terms of pads, street, and curbs.  I'm trying to get a feel for an average cost to build per unit.  My only exp is with detached housing.  

The finished product would most likely be 2500-3000 sq ft, two car garage, and finished very similar to a large builder's product.... nice finishes but not over the top.  A few recent comps of very similar product are selling in the mid 300's - 400k.

This might be a loaded question with too many variables but i wanted to check with the BP community regardless as the knowledge and insight here is always helpful.

Thanks to all-

James