We have debt north of 200k to include vehicles, student loans and credit card debt. 

When REI can not compete with other vehicles, like stock, REITs, bond, etc, money will leave REI.There might still be deals out there, for seasoned investors.

As  equity builds I pull it out to invest in other vehicles paying higher returns for diversification and reducing my risk.

This question and the answer can be complicated without knowing your long term goals and investment strategies.You should develop a plan identifying all your goals and what investment vehicles you will use then it would provide you the answers to needs. 

This sounds like your situation.As @Allan Rosso noted, a partnership or LLC agreement seems to be the best vehicle. 

Hard money is a short term vehicle and not something you would want to use to acquire a rental property for example. 

When tenants apply to rent any of my properties, I require them to list their vehicles.

You can obviously modify it to ask for make and model of vehicles. 

As a landlord, should I request the current tenant, without violating the law, to update me annually with new personal information like new owned vehicles license plates (when tenants changed their cars), changes of employment, emergency contacts, or someone on the lease turns 18, etc.?

Lets partner up to allow my success be your "good stewardship" and vehicle for more cash-flow!