If anyone has recommendations for free resources—whether it’s books, websites, videos, or anything else that could help me sharpen my skills—I’d really appreciate it.

I setup one QBO (Quickbooks Online) account to handle multiple LLCs. 

Theres a lot of place online to list like apartments.com, facebook marketplace, realtor.com, trulia, rent.com.

Go to Etsy and search for "rental property tracker," and you will find hundreds of nice spreadsheets to track 10-20 rentals, usually for under $10.Software has extremely helpful features like online payments, marketing syndication (click a button, and your property is advertised on multiple sites), electronic document review/signing, maintenance tracking, and owner reports.

We see so many Youtube videos with instructions on how to do self-closings/seller closings, and this saves a significant amount of money. 

@Annette Eck I’d send a complaint to the real estate board and the agent’s broker, especially if you have video proof that the agent is giving lockbox code to applicants, not present with them.

I'm not sure what you'd learn that you can't find online.

Sadly, it’s sat on the market too long and I’m looking to get creative with bringing the attention of many buyers looking for a good deal on a property (online auction or something else with tons of attention??)

Check out other online guides available here: https://www.biggerpockets.com/guides3.

We currently have 105 units and are using a variety of excel, google docs/sheets/calendars, apartments.com (ads and rent collection), docusign and QuickBooks online (which we would like to keep).