Being able to parallel path different leads seems valuable; somebody does my calls while I'm connecting with wholesalers / other agents, etc.

Our society no longer views elderly as valuable contributors to society because everyone is expected to retire at 65 and wither away in a corner somewhere.

A business model that has always made sense to me is teaching people how to find good deals and have them bring them to me for more critical evaluation and execution where I invest my capital beside yours.

It would also be wise to educate yourself on what a good PM does and doesn't do, how they do it, what they charge and why, etc.My book, The DIY Landlord, will be out in December and can teach you how to select or supervise a property manager.

These documents are the lifeline to your capital so as Jeff and @Chris Seveney have noted, don't skimp on the documents or the use of an Attorney to make use of the terms within those documents.I once heard Gary Keller of Keller Williams note that legal documents shouldn't be called 'agreements' but 'disagreements' because they only become valuable when there is a disagreement between 2 parties. 

Looking for what makes this location valuable.  

@Minnina Smith The Biggerpockets bookstore will have many valuable resources in it for you including some of the books mentioned here.

The simplest thing to do (at the risk of sounding like I'm teaching how to cheat) is to check the "material participation" box when entering a K1 into your tax software.

The passive losses will be valuable when you sell a property assuming it’s sold at a gain and you don’t want to do a 1031. 

Taking classes to learn how to be a real estate agent really just teaches you the laws and how to pass the test.