If you were going to focus your time on learning something, I'd say getting familiar with a bookkeeping platform (like Quickbooks Online) would be the best bang for your buck.

LLC is pass through income so have your bookeeper or CPA take care of everything at the end of the year for your tax documents.

What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

Build your network by joining local real estate investor meetups or online communities like BiggerPockets.

Does anyone do an online application?

You'll want to read Maryland new requirements for landlords.https://dhcd.maryland.gov/TurningTheKey/Documents/HB693-Land...

Plus, it integrates seamlessly with accounting tools like QuickBooks, making bookkeeping much more straightforward.Whichever account you choose, look for one with no monthly fees, online banking, and features like automatic bill pay.

Everything you need to learn/know is available online for free.

@Charles Perkins is absolutely correct about "collecting all receipts, properly tracking all income and expenses and your basis for all assets properly documented and recorded."

You should have documented that in writing, but even a text message from him would likely hold up in court.You post the notice and give them the required amount of time.