Also start networking to start buildign your team of find contractors, handymen, private lenders, real estate attorneys, title companies, architects,wholesalers.... 

The rep from their company that accidentally called me this morning was calling from Florida. 

Our company flips homes in Laguna Beach, and we operate student rentals (currently in New Orleans, but planning to expand).

The entire reason I hired a company is they are the experts and I expect them to take full accountability of making sure I am in the know and 100% compliant.

------------------------------------------------------------------------------------Recommend exploring as many sources as possible to get referrals AND cross-reference them to get as much accurate information as possible.Check out NARPM.com, BP’s Property Manager Finder (BiggerPockets: The Real Estate Investing Social Network), etc.Also, encourage you to learn from the mistakes of others - by reading posts here on BiggerPockets about owners not having their expectations met by their current Property Management Company.

(It's funny now) I hired a property management company and sure enough they told me the best qualified renter was the one who wanted to do a 9 month lease and pay it all upfront.

I'm building my portfolio of SFRs in Houston area, and thought I had signed up with the best property management company in town.  

Most serious and qualified tenants are searching on the major 3rd party platforms you mentioned + realtor.com, redfin, and a few others.Apartments.com & homes.com are owned by the same company and may offer some additional marketing options.Another strategy to consider here is social media - video marketing.

I have a great 1031 company I work with that has a lot of education and information if you want me to send it over. 

He's a partner in an STR management company and is very active in that sector right now in the Charleston area.