Quote from @Andres Lasaga: I am in the process of selling a property to the tenant I have been renting the house for 4 years.I want to outsource the promissory note collections and reportsIt would be only ONE property, for now, any recommendation of a company that can manage the collections and reporting?

They are free for 1 unit and then costs $9.95 per month for up to 10 units. 

@Kieran Collings - I'm an investor, flipper, and own and run a local property management company.  

I would consider getting out of property management and getting into cleaning IF you think they are doing better than you . 

Also, what are some other low cost amenities that I can add to my STR that will yield a higher ROI?

Call agents/property managers in the area you're looking to invest in for real time stats like rent and pricing info. 

Our needs got clearly defined last week when we tallied up the rehab cost on a midsized flip project, at $51k vs the $40k max we had budgeted.

., the actual management of the property & tenant play a large roll in how long tenants stay in their home.

I sponsor a monthly meetup of property managers based in DFW.

A manager will roughly cost $100-$150 a month to take over a unit (it could be more or less in your market) and manage the units.