Best software(s) and/or Apps to manage single family rentals (12) and 11 RV spots

Software recommendations to run RV park (11 spots) and manage 12 single-family home rentals. Software that's hopefully secure, easy to use and cost-effective. 

Financial:

Help with collecting and tracking rents that have been paid.

Integrates/compatible with Quickbooks Desktop.

Advertising to simplify and/or streamline the process.

Set up and aid in showing properties for rent. Tracking these conversations (text and/or email) and appointments.

 Note: I have a bookkeeper that does all the financials at her home, right now. I can see this may need to change.

Your thoughts and recommendations please.

Thank you, Joe Schultz