Well I would think this is something that you could do over time. Sure it's possible you could walk in at the right time and get accounts from them, but if you market to the over time it could increase your chances for results.
Maybe send a letter at first. Then go in and pay a personal visit to say hello. Then keep sending them mailers monthly. You want to build up their awareness of you over time so they learn about you and ultimately will want to work with you.
This process would be the same you would use with a customer base as well.
If your business is in the newspaper for a positive reason, one of your monthly mailers could show a news clipping. All these things would bring legitimacy to your brand and make the potential customer more comfortable with you.
If you REALLY wanted to work with them, why not once a month stop in with a pizza at lunch time and some sodas? Think about how much it would be worth it to you to land these accounts? Would such a move be warranted?
My opinion is that you will see very little, if any, results from realtors. Think about it, they dont own the house, they are just trying to sell it for the homeowner and it is the owners responsibility to keep the yard mowed. All the realtor does is show the home to potential buyers.
There are realtors that own the houses they are selling. *They're investor/realtors. *You could also talk with property management companies. *Maybe offer them one free mowing just for a sample. *Offer them discounts in your mailings to them if they use you on 5 or more properties... like maybe tell them you'll discount the services you provide by 5% for every 5 properties you get from them up to say 25% total discount (or something olike that, anyway).
Just make sure you tell them your service area and let them know that you don't want to do 5 of their properties and have all of them be on opposite ends of your service area (unless you are already in that area).