Additionally, you may need to have discussions with your JV partner to come to a mutually agreeable solution for the long-term ownership of the property.

This is a very broad question and without tons of additional info no one credible will be able to provide you a logical response.

Adding an additional panel for the second unit can cost between $5-10k.

Note that conventional loans allow 5% down for multi-families now...It sounds like even with your father's help, you still don't have sufficient funds, much less also having additional reserves...What, may I ask, is your job? 

I don't want to miss a good opportunity but I am also ok being patient - just trying to get all my ducks in a row, so I have the knowledge if something does come along - our credit is 800+ and we have about 900k in equity in our home with a 3.625 interest rate. 

Maybe a commercial line of credit?

You also get an additional benefit of depreciating the improvement/house over 27.5 years.

and what would this do to my credit score? 

These lenders often have more experience and flexibility with properties that include ADUs and JADUs.Community Banks and Credit Unions: Local community banks and credit unions may be more willing to work with you, especially if they have a better understanding of the local real estate market and the value ADUs and JADUs bring to a property.Mortgage Brokers: A mortgage broker may have access to a wider range of lending options and could help you find a lender willing to consider your property.

The Beltline does add some promise to the area and is currently under construction, but without additional supportive infrastructure, those markets aren't going to change drastically in the short term.