I'm guessing that it will be something like 10% to 20% but definitely not 40%.The one caveat on this is that for bigger buildings, the assessment is based on income approach, not market approach so they may not be getting assessed as high as the market approach. 

I was leaning towards the honesty is the best policy, not least becasue it is the much more simpler approach and potential tenants don't feel like they are getting scammed or I have something to hide.I will definitely be doing the Google voice number during the leasing process. 

I suggest that you first identify your goals and decide on the approach you want to take.

My initial thought was looking into the best approach (if any) with this lender to get one of these two specs at a discount which would get one of them off their books.

Also, an income stream is something that is likely to appeal especially to folks approaching (or already in) retirement.  

Is this a reasonable approach or is there a better one out there?

Once you have one half you can approach the owner of the other. 

None of these are recommendations since you'd have to talk with your financial advisor about how to approach each of these since they're nuanced but it's a starting point.

Your approach is wrong.  

The biz is still alive and well even though we're approaching the top of the housing cycle.Cheers!