Essentially the way it works is like this...The buyer puts forth the agreed to down payment, if any, and then takes possession of the property making monthly payments as per PSA.The seller retains title to the property until such time as the contract for deed is paid off or their is an earlier payoff per PSA agreement. 

This is pretty standard - any agency you interview with is essentially hanging your license for you.  

If you have a horrible tenant and you pay cash for keys you might be essentially sending him down the road to another investor who is going to encounter the same problems without having access to the information that the tenant is liable to not follow through on their commitment.

He could essentially get back that cost prior to 6 months. 

@ David Dachtera So does that essentially follow the same rules as a 1031 exchange would?

Fun fact: PMI is priced out essentially identically to mortgage loan interest rate pricing.

Of course, they generally don't assign a specific number to it, but that's essentially what they're doing. 

NOI is your nominal yield amount, the cap rate essentially provides you a yield % on your investment which provides clarity for comparison to other real estate options or dividend paying stocks or interest bearing bonds or any other investment which provides some form of cash return outside of simply appreciation.

"What other professionals(contractors, attorneys, agents, etc..) if any are essential to be connected with before making that first deal?"

Many of them are essentially re-packaging deals from the MLS, I would think it obvious that those folks won't be much use to an investor.A good wholesaler gets you deals that don't hit the MLS.