I ran the numbers by hand on a sheet of paper, now i want to double check it with the calculator.

You would have probably earned 3% Cash-on-Cash return with 20% down in the first year and doubled your investment before 10 years (i.e., income + appreciation).By the way, I assumed that the duplex was actually a single unit. $550K for two units would have been a steal ;-)Let me know if you need some help finding another rental.

I am looking to use my money to be a lender to an investor/real estate agent whom has a project to be started.I just received the contract and it seems pretty straight forward, but i want to make sure and double check i got my T's crossed and I's dotted. 

If you are trying to wholesale it, don't. 95% chance you'll just end up keeping their home off the market fit 60-90 days, so they can't sell to a real buyer, then the deals falls apart because you find a buyer, your double close doesn't work (no assignments allowed), etc, etc.

If I could add to what John Leavelle said  ; it could cost as much as $60,000 to do a full Rehab here in the Philadelphia Area        My Friend Sean just did a Rehab in the Port Richmond Area Close to Fishtown and he it was $60,000        Sean has done many flips and I thought he went as "Budget" as you possibly can , for an example ; he paid $7,000 for a brand new HVAC  (Heat & Air Conditioning)  with new duct work , where that would have been double in the open retail market       Good luck with the project & feel free to reach out to me if you need any help or have questions SincerelyRick      

Are there any wholesalers in the Fairfield County area that can offer any recommendations for closing attorneys who work with wholesalers and assignments, double closings, etc.?

I'd move a little further north in areas like Frisco, Little Elm (just double check school district) and The Colony.

I have the property under contract and will be closing with cash, I then hope to execute the additional transaction (sale from me to end buyer for the higher price), both transactions will be at same title company; double close.

You will find no better spokesman with a direct line to the seller (except for maybe you talking directly with the owner on an unlisted property) than an agent who stands to double end it if they close with you.

@Mike Cumbie gave you excellent tip, and I felt the response from I.B. was a double edge sword..