Follow proper landlord/tenant laws regarding posting/mailing notices. 

There are some unique challenges to investing out of state but they can be overcome with proper due diligence and working with the right people.

Yes, he gave proper notice and payment from what I could see.

You will want to ensure that you will be receiving the duplex in the condition it was in (or better) at the time your contract was executed. 

The fact they are complaining online might be an indication the property manager dealt with them properly so be sure to ask the manager for their side of the story.7.

@Elizabeth KnessHave your boyfriend execute a "lease" for you for $500 a month and go back to the lender.

I suppose its possible that you could see a property scheduled for auction, execute a contract with some sucker for a purchase price at $XX, and that sucker could put hundreds of thousands of dollars in cashier's checks in your hands, so that you could bid on their behalf at auction for $YY, and then collect the difference as your cut after auction when you put the property in their name?

Even if you went with a 3rd party online option to get the certified mail it can often come back undelivered & you'll need to send it out multiple times to ensure proper notice is sent.

Will is scale properly?

Nope):1 - Learn how to analyze with real numbers2 - Learn what a plan is, and how to develop one for REI3 - Learn what is important to a REI...and then start thinking like one, instead of a homeowner.4 - Learn how Money Works5 - Learn how to analyze Markets (not economic...geographic) in order to find where the properties whose profiles match the criteria you need to execute the plan you developed.6 - Learn how to eliminate any emotions, both yours and the ones you think are driving forces for the buyers/renters that will be your clients7 - Learn how to eliminate any for of "rationalization" (most expensive word a REI can use) from your thoughts.8...and last, for now, learn how to describe yourself (when asked what you do for a living) as a "Successful Real Estate Investor".