Susan Maneck I think you are spot on!! 

You might run into issues refinancing out in just 1 name (of the LLC has both of you on there) so you can take advantage of your 20 conventional loan spots between the two of you. 

Obviously that was my favorite approach because I am invested for the cash flow, but that had more to do with the profile of those deals than anything, so I understand why it wasn't possible (or smart!)

Everything shared above has been spot on!

I'm sure a real estate agent has a way to see delisted properties, in my case, I just have a small list of properties I've seen listed and not sold over the last few years. for unlisted properties, word of mouth and spotting vacant houses. 

You are spot-on.

The other option that comes to mind is to make it an addition to the 3rd floor and turn it into a 4 bed 2 bath two-level unit, but this is my least favorite option. 

Meanwhile other people are trying to lease the same spot, further complicating things.

I’m in the same spot... do I use an agent or marketplace to maximize my profit.

Like a spare tire, if you have a flat, you switch to the spare tire while you fix the real tire... just like that you need spare buyers so you can still sell your contracts while you fill in the empty spot with a new buyer.In order to have these spare buyers ready we have to deal with a factor of safety.