Breaking news: events in and out of our control will affect real estate both positively and negatively.

Correct, you as the "lender" have to control the contract as the buyer.  

We are willing to spend up to 500,000.

Some in our control, others not so much.

I would also make sure I controlled the checkbook or that we both had to sign the financials.

This allowed me to control renovation costs, streamline operations, and accelerate my investment growth.

I know its mean to say that people who do their own contracts get what they deserve, but you must know that if you are paying a couple hundred thousand dollars for something it just might have been worth spending $600 on a lawyer to do a proper contract for you.

In my opinion a fully passive RE investment is the most risky because you give total control to others. 

Worrying everyday about getting fired for something out of your control?

I know STR's are tough due to the tourist license's being heavily controlled/shut down in Barcelona.