If you have an "early buyout termination" clause in the lease he is free to use this option. 

I also welcome perspectives on utilizing a HELOC, other financing options, or keeping my primary mortgage-free.

I'm being told I have the option to buy it down to 5.75.  

I'm basically looking for something that glazes over or goes in depth about how an investor can set themselves up with as many options as possible to go about buying, but I can't seem to find anything.

There are other options like Citi and Navy federal that offer secured cards that graduate but some take a long time to graduate.

I like to get more options, current trends and pros/cons to start with investment .

Ok so buy and hold the home is my best option then.

ThxI think your best course of action, if the property is really worth it, is talk to a good real estate attorney and get your options and probability of being successful. 

A few things to keep in mind when obtaining an FHA 203(k) loan:1) Improvements paid for with a 203(k) loan must generally be completed by a licensed contractor and are subject to approval by an FHA appraiser as well as oversight by the FHA-approved consultant if it’s the standard loan option.2) You must develop a remodeling plan, schedule, timeline and put it in phases. 

Our only other option was to reject her as a tenant.