She has a lot of hustle and talks a great game about protecting my investment, streamlining procedures, etc. 

You are trying to protect yourself so that's understandable.  

What is the best way to protect yourself from running to any liens?

You are probably a "customer" which means they don't represent your best interests and have no requirement to protect you, negotiate on your behalf, etc.

It will also let you get to know the types of customer/ renter who would be interested in apartments/ houses in a particular neighborhood.

Knowing of course that it is an IRS untaught method to their people who Audit return (of our SIC codes)-- An unknown fish so to speak that might cause them to simply redline it costing the customer big Bucks $$$$$$$$$ (and anxiety).The tax savings on a $30,000 write off should buy quite a few Mcdonald's cheeseburgers.

As a Realtor, your contract should protect you (it does in PA)

Stay away from zero contingencies and get an inspection to protect yourself. 

Protecting your income, wealth and investments requires adequately layering insurances, and it is probably worth getting an expert involved.Best of luck.

So, how do you invest to (1) take advantage of property price appreciation and/or protect against inflation (devaluation of “fiat” currency) and still protect against a crash?