As for the billboard, some agreements make the landlord cover upfront costs such as new billboard banners or more importantly you might even have to pay leasing commission to a broker to help you get a company interested.

I'll give you a big tip: If you see ads or banners "Move in for $1, or First months rent free", the owner is struggling with vacancies!! 

On a for sale, it's days-on-market and much easier to discover.Working Las Vegas for SRFs, when driving about I saw banners like:move in for $1first month's rent freeThose concessions disclose a vacancy problem, at least in that neighborhood and more generally, in that city. 

I'm going to be the tough pill to swallow here...Anything passive, like direct mailers, bus stop banners, print ads., is all great and whatnot once you have already established yourself.  

An idea that I might try.Write a simple skinny contract of sale one for each propertyMake the contract subject to and contingent on third party assignment.Subject to lien and judgment report (you need to know what is in the chain of title)Get good comps, you need to know the estimate market valueNeed to determine the estimate potential equity Once you get a list of liens, attempt to negotiate a discount; write an option to purchase the liens at the negotiated discount.Negotiate with a local auction company to sell them at public auction; auction them all in one day.The auction should be a "reserve" sale, the reserve is UNDISCLOSED TO THE PUBLICThe terms of the auction; as is, all cash and subject to the approval of lien and judgment holders and record ownerUse banking days in your contract (gives you more time to close)Make certain you use an auctioneer who sells real estate regularly and has a god reputationQuestions to the auctions company; how often to you sell real estate, where would you advertise the sale (news papers, internet, radio, etc. for how long will you advertise, can you give me an advertising proposal, how much advertising cost will you charge me, how do you get paid 1. flat fee, a buyer's premium, seller commission, do you cooperate with agents, how soon can you have the auction, what size signs will you install (sign on the property should be large, maybe a banner on the buildings), how many directional signs will you install, what deposits would you recommend (too high of a deposit will discourage bidding), will you mail post cards to selected areas, will you hand deliver brochures to businesses in the area, will they be black and white or color, will you give me a list of all inquires receivedYour should preview the auction company's disclosures and contractsAuctioneer should disclose and announce at the sale that the sale is an assignment sale.Auction sales should be conducted in front of the house, inspection should be one hour befor the live All high bids should be taken (even if the price is way lower than expected, this gives you and opportunity to negotiate with all  in the chain of title

@Sean LarsonLet me fly the big caveat banner by stating that I do not know how easements are handled, or the time requirements are for a prescriptive easement, in your jurisdiction.Do you know where the property is?  

I saw a banner ad here on BP for Tenant Cloud.

CL, local FB, and have a banner hanging on the outside of the building.

@Bo Banner Find a property with enough equity in it, force some appreciation with repairs, then pull your capital out by refinancing it.

@Sunanda Nair we have a house/casita combo off Almeria right next to Coronado Park and Banner University Hospital.