The loan officer suggested a purchase line of credit with a variable interest rate and interest payments only to finance it.

There are many variables involved that will determine your best path to getting started. 

Of course like with any predication, it is subject to change as variables that are always shifting.

IRR is another variable you can use to get performance metrics/forecasts over 5 years, but generally, annual income divided by purchase price is enough to get a good idea how the property is performing. 

Plumbing and roofing seem to have the biggest variables-foundations too. 

I've used some sites but the ranges are so broad and there are so many variables that ultimately, analyzing the property becomes challenging - on the low end - bad investment; on the high end - good investmentThanks in advance

Something I've consistently struggle with growing up was sticking to the long term plan because it seems like there is always a new variable in the short term.

There's a lot of other factors and variables unknown here.

@Brad Neihardt it would have to built on an environmental anomaly, in a flood zone, be a historic property, or have active knob-and-tube to have a rate like that...but there are lots of variables Good luck getting some better rates

There are many variables by market and even by specific community that only local agents and property managers would be aware of.