@Jeremiah Mon education is vital but make sure you take action on the items you study.

Proving that an STR PM failed to live up to the PM agreement would be a lot harder.

For the first part of your question even if you were working with a realtor, I don't personally know many that have a true pulse on rehab costs and I wouldn't make any investment decisions based on their rehab cost projections.My suggestion would be to study how to evaluate the Big 6 rehab costs: roof, siding, windows, HVAC, electrical, and plumbing. 

Currently deciding to do it as a side hustle until it proves to be a worthy 9-5.

Print them off, study them, highlight them, make notes, read some blog posts, and understand the subject.The second document he links includes precise definitions and a guide for landlords to use for screening support animals.

.- Do NOT speak to a PMC that can't PROVE they also manage STRs.

Please study engineering and you’ll have more of a grasp of why measuring amperes (electricity) or volume (water or natural gas) lends itself to reasonable precision.  

Quote from @Jamie Hora: The question you pose in the title, "Is a rezone required if availability study can support more density". 

Due Diligence and Feasibility Studies - What studies or tests are essential before purchasing raw land?

Studying for and receiving the CCIM designation will be a solid plus.