The assumed mortgage has been fantastic as we got a good deal and have added lots of value by doing updates, increasing rents, and managing expenses. 

I have used Zillow and Zillow Rental Manager, and that tool is fantastic as it helps with the background check and tenant screening. 

If you go the DIY route, you *can* make more money if you manage to find a great deal, get a good contractor, etc - if you get all those moving parts to work together, this option can be fantastic.