I've been proposed something similar to this and have considered it.

Instead, know your skills and your abilities and use that to help them and propose what you could do to help.

I am aware of current Chicago proposal to more easily legalize garden units and this space looks like it would pass all code requirements or only need minor adjustments.- Order of repairs / updates (Musts vs Wants)?

I started with where I live, there are opportunities in every area, every market so I didn't make it a huge marriage proposal type epic decision to be made, I decided to figure out where I live and structure accordingly

So many people over pay for dumps doing what you are proposing. 

But make certain you have the SOR/WWU from the HUD approved FHA 203k Consultant first, prior to getting any contractor to submit a proposal, because the contractor proposal needs to be based on the Consultant's report. 

An attorney could also answer this in a second - and would prob propose a remedy cheaper than an actual eviction. https://www.revisor.mn.gov/statutes/cite/504B.271

Your LOI should clearly state your proposed timeframe for due diligence period and closing, in addition to price (of course), earnest money, how you intend to finance, etc.

Please clarify if the existing three baths are all full baths, and if your proposed fourth would also be a full.  

Proposed pets (size/breeds)4.)