With closing costs and other minor items, I figure I'll end up about 74k all-in. 

(not to mention that the land lease is behind and increases every 5 years)Here are my questions (what I am trying to figure out):- is there any way/chance we, being a cooperative, can still direct the responsibility of the interior unit maintenance and repairs to the unit owners without converting to a Condominium (which is not an option due to cost), i.e. make the owners responsible for maintenance and repairs of their specific unit?  

Just because someone in a commercial transaction tells you what a cap rate is, you still have to figure out for yourself if that cap rate is realistic. 

He will want to stay involved with the property long after his financial investment is paid back, to get the most bang for his buck which I'm fine with, but I want to create clear expectations for his future return. 

Being we need to be as creative as possible, I figured I would charge an inexpensive amount for the listings to get started all while helping others…. 

I called a local Keller Williams agent today to help me sort all this out, find out some figures and begin the conversations.

I am an agent as well and have access to mls  and am confident about the comps, so I don't expect to have any trouble finding a buyer for them they are solid deals . 

This is a self defeating question and from the sounds of it you are already expecting failure. 

--First and most importantly...generally speaking, when are peak rental seasons and how many weeks per year can a good mountain cabin be expected to rent in the area?  

I know a lawyer could figure it out anyway if they really wanted to either way but if I'm in the mix anyway managing the properties I don't see the difference.