It is not as easy as those promoting it would have you think.

SO---ARGUABLY, and it's true too---almost everything we do can be traced back to some sort of activity on one of those two business pursuits -  lunch with client, assistant, or prospect.... and dinner/drinks with the band or promoter. 

They constantly offer zero interest promotions.  

See if any of the local colleges or social service agencies have any programs that you can promote or even pay someone $100 to come teach a few classes. 

Self promotion isn't allowed here, so that's all I'll say about that.

You could use balance transfer offers, as long as you are able to make the payments and transfer or otherwise pay off the balances when the promotional period is over.

Anything you find is going to be either so high level as to be meaningless or paid content to promote a particular provider. 

I've heard an interesting tip on a podcast once where the owner had out of state properties and property management in place, but whenever there was a vacancy he personally promoted the crap out of it on zillow, redfin, craigslist, facebook, etc., regardless of what the PM did.

Here are the laws in regards to this stuff.4735.01 [Effective Until 3/20/2019] Real estate broker definitions.As used in this chapter:(A) "Real estate broker" includes any person, partnership, association, limited liability company, limited liability partnership, or corporation, foreign or domestic, who for another, whether pursuant to a power of attorney or otherwise, and who for a fee, commission, or other valuable consideration, or with the intention, or in the expectation, or upon the promise of receiving or collecting a fee, commission, or other valuable consideration does any of the following:(1) Sells, exchanges, purchases, rents, or leases, or negotiates the sale, exchange, purchase, rental, or leasing of any real estate;(2) Offers, attempts, or agrees to negotiate the sale, exchange, purchase, rental, or leasing of any real estate;(3) Lists, or offers, attempts, or agrees to list, or auctions, or offers, attempts, or agrees to auction, any real estate;(4) Buys or offers to buy, sells or offers to sell, or otherwise deals in options on real estate;(5) Operates, manages, or rents, or offers or attempts to operate, manage, or rent, other than as custodian, caretaker, or janitor, any building or portions of buildings to the public as tenants;(6) Advertises or holds self out as engaged in the business of selling, exchanging, purchasing, renting, or leasing real estate;(7) Directs or assists in the procuring of prospects or the negotiation of any transaction, other than mortgage financing, which does or is calculated to result in the sale, exchange, leasing, or renting of any real estate;(8) Is engaged in the business of charging an advance fee or contracting for collection of a fee in connection with any contract whereby the broker undertakes primarily to promote the sale, exchange, purchase, rental, or leasing of real estate through its listing in a publication issued primarily for such purpose, or for referral of information concerning such real estate to brokers, or both, except that this division does not apply to a publisher of listings or compilations of sales of real estate by their owners;(9) Collects rental information for purposes of referring prospective tenants to rental units or locations of such units and charges the prospective tenants a fee.

Regulation S allows us to solicit anywhere outside the U.S. directly or via international agents who can also generally solicit - however some countries may have separate securities laws which may impact how or where they may promote.