I'm also wondering what type of properties people have been successful with (single family home, small condo projects, or large complexes).

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.

Choose one, try it out, and see if it has all the features you want.

I lived in 4 different apartment complexes during college, and this was my experience as well.

Here are a few suggestions on how you can maximize the wealth of information available: Check out the blogs and podcasts, or take advantage of the search feature (magnifying glass).

@Deborah Lee these range from free to various costs, depending on the features you want:Doorloop, Hemlane, Innago, RentRedi, Stessa, Avail, Apartments.com, TenantCloud, TurboTenant, Buildium

Question though - why have you decided to create this multiple tiered structure and so much complexity? 

But they're really not that complex or expensive.

The ability to work with unique or complex property situations?

Collecting rents is super easy and the bookkeeping features allow me to track all revenue & expenses for each property in a manner that makes filing my taxes at the end of year very easy.