Good luck- shoot me an IM if you'd like more info on my process..a little bit of background research and some phone calls can make your sq' price swing back a lot. 

They are generous on the values so sometime my actual cash out of pocket is less than 15%, for example, I pay 102K for a house that appraises for 108K, the extra 6K they count towards my down payment so I get a mortgage for 91,800 because that's 85% of 108K and I write a check for about 10K.

During the due diligence process, did the buyer walk the property, unit by unit?

To discuss other side of this thought process on new builds..

For the historic district, I would just make sure that you fully understand what requires approval and what that process looks like.

When I have provided it, I write it in the lease that it's not included in the lease and I'm providing it as a courtesy only and if the tenant wants to use it they may and if it breaks down, I won't be replacing it.Allen

I would strongly recommend spending the money to meet with an attorney for an hour before you put anything in writing to your tenant.Good Luck!

-repeat the process every year by acquiring one house every year with the appropriate income qualification

Always formalize the agreement in writing to define costs, profits, and contingencies clearly.Let me know if you need help structuring the deal or exploring funding options.Best,Drago

Ask the seller's agent to put their counter offer in writing.