Or are there classics that still hold true for today? 

It looks like you've been in contact with the seller and may have a gauge on their true desire to sell, which can help you determine whether the $600 for an appraisal is money wasted or a worthwhile risk.My supposition is the appraisal will come in higher than your offer, which will likely embolden the seller to stick to the appraised value or higher.

Their true vacancy rate was roughly 13% not 1.5%.

I have a property manager so I don't need true property management software. 

Any thoughts on different techniques I haven't thought of?

Gary, I have done this technique in the past and would tell you it is extremely effective.  

I find out from other who have done this what are some of your experiences, techniques, reasons etc.

People say anyone can do it, which is true, but not everyone is willing to do what it takes.

This will help you with your test taking technique for the exam.

Nobody likes to tell women that nowadays, but it's true.