I have about $15k I have to pay back for school.

You're just using new debt to pay off old debt (which is the same concept as your alternative: refinancing your primary to pay off the HELOC).

Let me know what is the right path for us - Trust and sole proprietorship OR trust and LLC OR something else? 

Patience does pay out.

Then reinvest all the profits for myself and the money lender until we reach a future goal ($600K).The question is, if the money stays within the LLC then I assume that I am paying roughly 20% corporate tax on all profits from each project.

Besides wear and tear on the building and furnishings, remember with MTR you are paying for all utilities, internet, and lawn care, unlike LTRs. 

You might want to listen to some of the BP podcasts on some of the other ways that real estate "pays" you, outside of cashflow.Keith Weinhold from Get Rich Education also has a good podcast and regularly discusses the 5 different ways that real estate pays you. 

He even had former employees hire the contractors, so when he didn't pay them, they couldn't sue him but ended up suing is poor employees.He has bragged about never being able to be traceable because he sets up his LLCs in such a way he can operate without legal ramifications,This man has no moral compass and has stolen the retirements of so many people.He did all of this so he could fund his new syndication business MENACE CON, with his other partners Nicholas Trevillian and Jason Von Payne...

The listing shows that it has the potential to cash flow around 5K per month after paying for the loan.

The property is held in a living trust, could I add my LLC as a beneficiary to the trust as to not trigger due on sale?