@Matt Wanyes but... is that actually your biggest concern? 

My biggest tip: research, research, research. 

Maybe the biggest "risk" might be the fact that you cannot occupy the property at all so technically if you run into hard times and need to move into the property thats not intended - but no real more risk. 

@Tamika Davis One of the biggest advantages of most software on the market is to complete these tasks you mention (maintenance, leases, rent collection, etc). 

Having time to do the work was the biggest benefit.

What were the biggest line items?

I stayed in touch with all of my investors who bought off of me to see how well they did and my biggest joy was when they returned to buy more or told their friends about me and what I do! 

My biggest client today is a seller I didn’t even represent during his sale of a 24-unit building—he had another agent.

But in general, your biggest risks are not necessarily what's the maximum rent you can get, but can you find a reliable tenant that will always pay and pay on-time.

Your biggest resource will be from people.