I will add wholesalers to the list of people to talk to and I'll look into getting some sort of advertising.

Lower-income areas will always advertise higher returns, but whether those pan out are another story.

For instance, search the local rental listings and see if they are offering any concessions (they are not always explicitly advertised).

Those include insurance, vacancies, eviction costs, tenant damage over the security deposits, a CPA, a lawyer, HOA assessments, make ready costs between tenants, advertising, etc., etc., etc.

I am currently 100% occupied in all of my properties w/ very litte effort or advertising.

I haven't done enough research to answer that question, but it seems that as long as it's not advertised generally, then it's legal.As an Agent or Broker, you will have much more qualified Contacts available to you for these Wholesaling opportunities, I believe.

Most syndicators don’t advertise, their client base grows by word-of-mouth and referrals.

You could always post to the marketplace on here and advertise them as Turnkey.

They are quite easy to find on Craigslist, Zillow, use Airbnb as free advertisement with a 30 night minim stay, or get with a realtor to post it for you but my personal suggest is to throw some furniture in there and rent it out for $4000 - $5000/mo using Airbnb or corporate rental. 

I spent $9.95 on Robert Allen's, "Nothing Down", (when it was first published ;-), $50.00 for a used cassette tape series from Tom Hopkins on "How To Master the Art of Selling"$100 for a used Carlton Sheets Audio CD series (I forget the title)$19.95 for "The Pre-foreclosure Property Investor's Kit" by Lucier, $18.95 for "Making Big Money Investing in Foreclosures" by Conti & Finkel, spent multi-thousands of dollars in advertising doing pre-foreclosures and fix & flips and making a cool mil in profit, in addition $1,599 for John Burley's (2) 3 day live sessions (6 days total) on "Creative Financing" including CD's and contracts, (which was awesome and well worth it, but then, I actually apply the information.