It's not too hard to make the building habitable by adding a shower.

preventative clause in lease: "property is rented as-is except for conditions affecting habitability"

They shot it down pretty hard - no habitable space is allowed in detached structures.  

It’s agreed that lower demographic properties have greater volatility and a much greater chance of having a disappointing (if not outright negative) ROI for longer stretches, due to evictions, turnover, lack of good tenants due to high unemployment, and general social pathologies and bad financial habits among the lower-income tenant group.

You may get an offer you can't refuse immediately, or you may have to go through a long process to do your build to suit.Without knowing the area and the accompanying demographics and growth, regional and national tenants may or may not be a possibility.A "lease/purchase" type of agreement is fraught with hazards; as, some courts have handed down rulings that have harmed sellers entering into such arrangements.

If you're asking, do you have the right to sue them for breach of contract or seek damages for the harm they caused, then my off the cuff response is no.

That can basically be my down payment for a tool shed.I agree that you should watch your spending habits but the truth is, it's about building your network.   

At that point I received angry text messages from the buyer's agent calling me names and wishing harm on me. 

And if it's not "habitable" as-is, how about adding a 203k reno loan too?

Get in the habit of finding properties and going to see them.