When the 2nd plumber came out (with the same company), he said the cartridge was not seated due to there being some calcium that needed to be scrapped off and no new valve was needed. 

It's best to start in your own backyard, but if your immediate area has less than 400,000 residents, then consider going to a virtual market- Connect with as many agents, contractors, property managers, attorneys, and title companies as you can.

Anyone have any insight on companies/individuals who rent properties for this purpose?

I agree with @Trenton Lukenbill that maybe it's time to start thinking about the next property management company.

It is a growing area that is right on Highway 32 so it is continuing to have new businesses and companies moving into the area.

I am looking to buy a SFR and want help from a Property Management Company to manage it.

In all seriousness they are a customer service company that just so happens to be in real estate.

Once the pressure is gone and the knowledge comes around, we wouldn't mind taking on a bigger complex, or possibly owning our own property management company. 

Asking the sellers to repair the whole roof is quite common, sometimes their insurance company will repair it for them!

Or what software/company do you use to obtain background checks on your tenants ?