LOI from Private Money for Proof of funds?

[Jeff Bridges]

I am in the midst of orchestrating utilizing capital from partners and/or private money with notes to submit cash offers for properties. Do I have them create a letter of intent with a defined figure representing the money they are bringing to the table when I submit and offer? How does the bank usually respond to cash offers amongst partners or private money. Do they just need proof of funds from the lender account regardless of who is on the bid contract? I know its a sensitive issue to submit bank accounts and would like to get it sorted in advance.... Thanks!