Given your financial constraints and the property's ineligibility for historic tax credits, this approach allows for reinvestment into assets more aligned with retirement account rules.For future real estate investments, you don't need an LLC for tax reasons.

All of those people also get credit/background checks. 

Take out an equity line of credit on the property that can be sides as the down payment for the primary residence.

I can do that for you if you are properly prepared with reserves and credit.

That way, you might preserve some of your monthly profit while still knocking out that line of credit.

But without the experience, knowledge and capital (actually CREDIT CAPACITY) I accumulated the prior 2 + years, this transaction would not have been possible.

I am considering doing this with a 0% APR credit card to avoid a loan. 

The credit unions tend to have lower fees and offer solid business products.

As long as the rents can cover both the current PITI and proposed P&I payment, credit is at least 680. you should be able to qualify. 

Another option could be a home equity line of credit (HELOC) if you have enough equity in your primary or second home.