They own about 900 lots in Jacksonville to develop still.

I am the Developer for this project with the intent is to turn an old factory into a 20-25 unit apartment building.

I would develop an escape plan which may involve finding a great deal if you can fire sale if needed.I am not going to comment on the cities you mentioned but they are very different in size and opportunity. 

I am not familiar with NH but it appears that the developers are rezoning it themselves and then building.

Flipping and wholesaling are not the easiest startegies for starting out - both are active jobs (as opposed to an investment) and require a combination of different skills that need to be developed and take a long time to master.

My question is: What is the best way to find an investor/developer/buyer to purchase this property.

He brings a tremendous amount of knowledge in creating and developing relationships, underwriting deals, and creative ways to finance deals. 

Those you listed will definitely be in the consideration set for buyers looking at our area but they’re not apples to apples comps, given they’re mostly newer construction and in HOA developments vs ours being a standalone single family with longer history.

I'm very new to the idea of rental properties and after some initial research I would ideally like to house-hack a MF south of Aurora.

And ideally you will eliminate the HELOC balance at some point by either refinancing into a fixed rate loan, selling the property for a profit, or by some other means.