The house is in very good condition and there is minimal deferred maintenance.

Take a look at the expenses: are there ways to minimize maybe by offering a cable package or from Water Bill perspective, installing water-efficient plumbing.

It's a newer condo so repairs are minimal (appliances here and there and a plumbing issue here and there).it's in a good school district so it should always be easy to rent, but value is very flat so appreciation looks like it'll be minimal moving forward.Thank you!

I know all of this to be true but am no way qualified to give real life numbers and that is what my parents will require to do anything other than just making minimal updates to allow the property to limp along.

You did not mention the type of investment or how the split is handled on revenue or losses (33% to each member of the JV.  

If you need to have an empty building, then you should account for loss rent during the time of reno.

If I'm correct, of the two  I believe the attorney's opinion is better because the attorney and more importantly his E&O carrier, if he has one, would have liability for a covered loss you might suffer for relying on his opinion. 

We just realized that we need to do our part and minimize exposure.   

Buying now and selling in 4 years, you will probably have to take a loss on the duplex if that is your strategy.

If anyone has any advice to make this process easy with minimal risk, I would appreciate the info.