So if I understand this correctly they essentially get to build a better score because they are an authorized user on your account but they never actually get to use the cars, is that correct?

There are over 20 real estate accountants on this site.

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

We have a few STRs that we have done cost segregation studies on.

While you will need an engineering company to complete the Studies, you will need a tax preparer to file Form 3115 to do the catch up, as suggested above.

Study the market.

Remember that if you later take over and manage it yourselves, you'll need to start a new account from scratch - your previous reviews with that property manager won't transfer.

It’s an excellent bookkeeping, accounting, and rent collection tool specifically designed for landlords and investors.

Be accountable. 

For example, some hard money lenders will require that the person financing hold a specific portion of the LLC (20-30%+), especially if the funds are coming out of their account directly.