As it has been said, you need to go and drive the area and make an assessment for yourself to start with. 

Although the majority of Michael's superb content on Cost Seg focuses on how to properly assess the value of Cost Seg, he also does highlight some items regarding the internal workings of a Cost Seg study.

Long story, it was through a real estate agent, but the owner determined his price assessment of $150K is correct, and the agent wrong.

I believe they do free assessments if you wanted to get a second opinion. 

Then possibly get hit with a $100k special assessment while you have it?

The county assessed value means NOTHING.

Use it to quickly assess properties and estimate renovation costs, which will help you make smart offers.Join Local Real Estate Groups: Get involved in local investment groups.

A good starting point would be to assess the type of investment property you want to get in to.

I agree with most of your assessment regarding Florida's real estate market.

It’s just the valuation.If I don’t fight this valuation, I am paying taxes on a higher assessed value than what I bought it for a year ago (they do 5 year assessments) and it’s effectively a 40 percent increase in taxes vs 2017.