For non real estate investor partners, consider their alternative options, and be in range.

Not having any luck finding my buyer a flip on the MLS, so I was looking for alternative ways like reaching out to wholesalers. 

Can anyone help me out on a way to explain this to him without hurting his feeling or give me an alternative way to still make this seem like a valuable option for my brother without giving up such a significant portion of the equity in the property?

Alternatively, find a good handyman (person) who you can hire for a day each month and get them to go to the units and do minor repairs.

If you can clarify what you're talking about there, that will help us offer some alternatives to consider.

Issac - I guess I never thought of a PO Box as an alternative.

(Alternatively, you could set up a single member LLC to own your 50% of the properties). 

The other money is invested in either your business or alternative assets so I wouldn't repurpose a lot of that unless there is no point to it or no return.

or have any alternatives?

This might involve debt restructuring, seeking alternative financing, or even offloading non-performing assets.