Tons of turnkey providers from various markets represented here on Bigger Pockets.

I would start with a Independent agent with multiple markets (companies they represent) and have them shop it for you. 

When you buy with cash most of what you are seeing is artificial cash flow from your own equity and does not represent the cash flow from the property itself.

Roll that into a 30 year fixed rate loan, and only put 20% down, then being represented by a professional is pretty small potatoes.

But the LTL in your proforma would be $300 which represents the difference between what the units are rented for (on average) and what you can get once you buy the property, manage it right and bring rents in line with the comps (assuming that you were correct in your analysis, the other manager's weren't misleading you, etc).So the lesson here is that you can't make decisions based on the Market Rent shown on the rent roll. 

They would represent me on the sale when, or if, it goes that far down the line. 

Your parents can sign a POA (Power of Attorney) that covers their real estate, or just that one building and then you would have legal right to represent them even in court. 

I just read a debate on whether or not to use a Buyers Agent and if I were to buy something she shows me she would be representing the seller and me, the buyer. 

Hey all,I'm in the process of getting my RE license but have already started to casually connect buyers and sellers on some deals that normally would be represented by a broker on one/both sides. 

HOWEVER, I’d be careful to represent the seller, check your local laws or talk to people doing this in YOUR market.And here comes @John Thedford