while I totally understand the frustration especially purchasing what was supposed to be a new and ready to go asset, but these things are pretty common so don't feel to discouraged. 

On the other hand, you might find a common reason that a few of your potential investors are not investing that might change your own thoughts on the deal.

This is the scenario you would want. 

There's also a calculator on my website that will help you navigate different scenarios.

No shame in either scenario! 

As indicated I cannot see a scenario where the housing shortage is not exasperated.  

@Gary Abrams A cloud based solution would work really well in your scenario of having other family logging in and helping with management. 

Should I try to make the deck on the second floor a common space or as part of a large bedroom?

@Brandon Croucier is giving you solid info on finding an experienced and honest mortgage broker who can shop your exact scenario both ways, with the rehab and without and break down the benefits of each with all fees so you can see an apples to apples comparison. 

This is a very common way for people to investing using their retirement accounts.