The lender needs to know way before the closing table that you have enough to purchase the amount in your bank account (including Closing Costs), another issue that they'll would have even if you could do that is projecting DTI due to that high balance as soon as you close on your credit.

Just get all expectations including yours on the table so everybody stays happy. 

Those are just table stakes to get in the game. 

I've also had a line of credit put on the table as an option for an investment property.

I understand these parties can help, but I need to bring a contract to the table for this project as a next step.We can potentially build 2 air b & b units @ 120/night for say 20 nights a month (these are allowed and active in the area at that rate).

You will look at the Table of Uses and make sure that "Multifamily" use is allowed.

In terms off using hard money it's a numbers game and totally a possibility, I have used it for a BRRRR and am using it for another I just closed on, keep in mind you usually have to bring just as much money to the table as getting a conventional loan, you just have the flexibility to pull it all or some back out when you do your refinance if you can make your numbers.

If that lender has other options that he can clearly make a better return on, and he can prove it and show it to you: rate of return, amount of dollars to the stock market, what everyone in that area is doing, that they're all making money investing in a local business or whatever, then the only way you're going to get him to come to the table is if you're offering a greater return than what they can get elsewhere with a lower risk.

@Philip CookSounds like you have it covered.One option we did to make sure an offer stayed on the table, was to put $10,000 down non-refundable towards the purchase, subject to zoning approval within 90 days. 

They would be taking on 100% of risk for 50% of profit, not fair in my book if I was in your shoes.As an example, I funded a deal via partnership (mini syndication on one single family home) where I had zero money in the game but I did bring to the table a lender who funded 80 or 90% of the acquisition price and the "partners" who were silent (only involved via financial) received 65% of the profits at the end.