Their representative recommended I engage with JP Morgan Chase private banking / wealth advisor as they thought this would allow them to be more creative and include other assets as part of the collateral.

Private financing where an investor can get a loan from an individual rather than a conventional loan because you can get more leverage and have more room to negotiate

You could pay them a flat interest rate on the funds they contribute, similar to a private lender, or offer a percentage of the profits to align their success with yours.

Hard Money Loans: These are short-term loans from private lenders based on the property's value rather than your credit score.

Investing as a limited partner/ passive investor is a somewhat risky endeavor whether it in private placement or in the public markets.  

From a compliance stand point, seller financed notes have much more leeway, fudge room, as they are looked at as private transactions.

I know I can reach out to some mortgage brokers to connect me with a private lender for most of the mortgage and then I would just need another lender to supply the down payment and renovation money.

Strictly from a private money lens: If you're open to a 2nd position private money loan against your STR's, it's possible.

If it's private money, they would issue a letter.

However, depending on the Trust Company you work with, you might have more options with respect to the diversity of public and private market investments.