Half a year later, here I am introducing myself to you all after having read more books than my previous fifteen years put together and devouring every resource I can find, including no less than half of the BP podcasts (almost all played at 1.5x speed; thanks for that epic Quick Tip @Joshua Dorkin and @Brandon Turner).

I have a long standing relationship with my credit union. 

Go to a local credit union.

Should I start with any credit union or Lendingtree.com etc or any other source?

And you're probably going to pay 3 points or so upfront for that hypothetical hard money 2nd mortgage on an investment property to 70% CLTV, assuming you could get it.I don't have any credit reports in front of me, but I'm pretty sure you can do a little better than 4.83% at a cost of three points.

Any study guides or tips would be greatly appreciated!

Along with a credit report, I have read that other documents for a rental application should be included.

I have 750+ credit and zero other payments. 

I am trying to soak in as much information and advise as possible while working my full time job running a doctor's office, so any tips and information thrown my way would be very much appreciated.  

Thanks for the tip man!