How can I find my neighbors lender without asking my neighbor?!?!

[Adrian Macias]

I have a neighbor that is developing a duplex next to my lot. 

He wants to go 50/50 with me on my lot and build an exact same product. This will help his property appraise for more and have comparables nearby. 

He isnt interested in building it for me, and charging me a fee. He doesn't want to share any resources either. 

I own my lot free and clear and would like to leverage my land as the down payment to start the development. I feel like I can build a similar product and give away less equity in doing so. 

I want to build and hold. Anyway to find out who their lender is.

Or any recommendations on a lender who can help me?