Not knowing the age of the wood you are speaking of, I am going to take a guess and assume that the pine is fairly old.  

In your OP, you said references were great - what type of references were they, and how did you go about verification of them?  

You will want a completed financial statement, last three years tax returns, real estate investing resume, spreadsheet of all your properties detailing the address, age, size, cost, value, rent income, expenses of each house, pictures.  

Amex upped my credit limit to $35k without income verification or anything!

In this particular case the tenant taking over the lease that ended up disappearing was a Captain, go figure...Deadbeats come in all different ages and income brackets, and if they are military just because they are high ranking doesn't mean they pay their bills and fulfill their contracts.

I just turned 23 on Jan 27th my goals are to start and keep flipping homes and  own at least 5 rentals by the age of 30 so building my credit is definitely necessary for those long term investments 

A needed to do yes, but not like it used to be.It's a great deal depending on the utilities.Home age, you want old homes actually.  

Income verification...

Maybe that's just old age and bad memory

That is the age that mandatory withdraw from retirement accounts begin.