Check out the STR forum where you'll find some great information and will see questions and answers from those who have successfully scaled STR businesses. 

Private money may be better. 

Quote from @Gregory Wilson: A few things there, Brendan.First, an LLC with you as a member and your (wife, son, pal, etc.) partner as a 1% member will file a Form 1065 which is about one tenth as likely to be audited by the IRS as a Form 1040 with a Schedule E rental activity (which I presume you will attempt to show is an active business).Second, you want an LLC because when your local Alabama handyman drives his girlfriend's uninsured truck into a van load of U of A medical school interns on I-22 when he goes  to get some shingles for your roof, on your business, you don't lose everything you have or ever will have to an uninsured claim. 

It’s important to ensure you’re comfortable with these risks and consult a financial advisor.If you choose to use a HELOC, consider traditional financing or private loans as alternatives if you prefer not to risk your home.As for your first rental, markets in the Midwest and Southeast offer great opportunities with turnkey properties that are tenant-ready and appreciating.

It did fantastic and I parlayed the profits into growing the business I have today.But that was 2016. 

I almost fell over dead thinking maybe I was going into the wrong business.

I am a general business major and also currently working on obtaining my real estate license to become an agent.

Is the way these lenders do business?

The risk of "piercing the veil" applies more to LLCs when personal and business finances are not properly separated, not necessarily to individual landlords renting a portion of their home.A more practical approach is ensuring you have a solid lease agreement, sufficient liability insurance (including an umbrella policy), and properly reporting rental income and deductions on your tax return (Schedule E).

It would seem that turning a real estate training program into a successful business is very difficult because most of them are not around any more.