The street the duplex is on is sprinkled with mainly single family homes in the range of 650K-1.1M.

The normal range that I pay is between 9-13%.I can't recommend someone at this time because most lenders have told me that their money is fully lent out or others are holding back because of the uncertainty. 

Most are cheap sheet metal sides and back in rural type area or remote towns and have limited growth in dirt value long term and if dollar store ever leaves almost no tenant wants the building because of the poor construction.People buy them because investment grade tenant and it's about the only thing sub 2 million in price in the 6 plus cap rate range.

I've seen stuff in the $2000 to $5000 range but you're taking a big risk if you don't get things set up properly.)Before you search for an attorney that specializes in drafting these documents (and spending the money that entails), you should have a clear idea of what your business plan will be.

What is a reasonable cost range for a lawyer to handle this task?

The current 30-year rate is 4.5%, new rates will be in the 3.8-4% range for a new 30 year loan.I will do more research and talk to professionals, but general advice is welcome. 

Rents are expected to be in the $1,100 to $1,900 range and while that does feel a bit high for the market, if these units are higher end and offer nice amenities with multiple bedrooms I think they will rent. 

This basic communication is for a large commercial building with multiple tenants ranging from mom-n-pop to national chains. 

There are many more comprehensive underwriting solutions for multifamily buildings.

And yes you can hire a professional estimator but just be aware they range between $125 and $250 an hour.Caveat, as with any profession that involves a professional opinion you're going to run across people who are more and less expensive than the book.