Simple question here: with the interest rates being as low as they are how does this impact the percentage of purchase price you should look to charge(earn) for rent?

There is a hold period required to capture the full benefits of the OZ. 

Pretty simple. 

It is a pretty simple process.

I guess my question is it as simple as drafting a new promissory note and recording it or am I missing something.

It could be something simple like a leaking supply line or a leak from a rocking toilet.

So while you recieve the benefit from them over the course of 27.5 years, you do still receive the benefit from them.You'll want to amend your tax return to capture these holding costs correctly.  

Simple answer for me, but all things considered who do you feel most comfortable living with?

This really is simple. 

The simple answer is that in a tough market to find deals you need to look at more deals in order to get one.