Perhaps there is a realtor association that has this information?

The STRs after all associated costs (including PM) are underperforming LTR at market rent.  

My ultimate goal is to house hack a 3–4 unit property.I’m seeking advice on how to accurately estimate the closing costs and monthly expenses associated with a multi-family property.

I think one of them offers a public API.Once you get your license, you can join the CAR Chicago Association of Realtors and I have found them to be extremely helpful with questions like this. 

I have used Prop wire for some skip traces, but the numbers and emails it provides were not associated with the property.

Next Saturday March 4th, I'll be teaching another seminar on everything PadSplit, hosted by Georgia Real Estate Investors Association (GaREIA) at their main office.

Yes - you should budget all the associated "costs" with the rehab including renovation costs, holding costs, selling costs, etc. 

STR means higher liability and risk for the property owner since it is often associated with higher insurance costs, more transient tenants that are not always viewed favorably by neighbors, as well other issues and risk.

Hey Gi'angelo, I recommend checking out your local REIA (Real Estate Investors Association).

The company making the offering must take reasonable steps to verify that an investor is accredited, which may include checking financial statements, tax returns, or receiving confirmation from a broker-dealer, attorney, or certified public accountant.These regulations reflect a balance between making capital more accessible for businesses and protecting investors from risks associated with unregistered securities.