My concern is that if i apply for a HELOC to use for the down payment before i apply for a mortgage, A) I wont get approved due to my DTI ratio, and B) I wont get approved without first showing the bank I have the 20% down payment before pulling the HELOC.

You may want to find a private lender, sell something, etc…The mortgage lates are going to keep you from any bank/mortgage products

There are also additional costs of operating and maintaining an LLC, like separate bank accounts, annual report filings, tax filings, etc.2.

The bank is going to want to know that.

Your local credit union or bank should be able to help you with that 

Quote from @Jamie Banks: @Jason Tucker Yes, you can't turn them away because of their sex but I've seen some investors who have multiple rent by the room properties "refer" someone to one unit vs. the other.

As of my last update in April 2023, the definition of an accredited investor includes, but is not limited to, the following:Income: Individuals who have had an income of more than $200,000 (or $300,000 together with a spouse) for the past two years and expect the same for the current year.Net Worth: Individuals with a net worth exceeding $1 million, either alone or together with a spouse, excluding the value of the person's primary residence.Insiders: Directors, executive officers, and general partners of the company selling the securities.Professional Experience: Certain professional certifications, designations, or credentials or other credentials issued by an accredited educational institution may allow an individual to be considered accredited.Knowledgeable Employees: In the case of private funds, "knowledgeable employees" of the fund are also considered accredited investors.Institutions: Banks, partnerships, corporations, nonprofits, and trusts with assets exceeding $5 million.By imposing these criteria, Regulation D is meant to ensure that all participants in such an offering are capable of fending for themselves or sustaining the risk of loss, thus requiring less regulatory protection.Under Rule 506(c), it is not enough for an investor to simply claim accredited status.

You can do a subject to transaction but that is not legally assuming the loan.the banks got rid of assumable mortgage long time ago. 

I have a clause in the lease that says the security deposit will be held in so and so bank with so and so address and interest rate will be xyz.

In most states all you need is a separate account in a bank in that state.