I believe there is probably money that can be made from real estate companies. I think a different approach could be more effective. Instead of mass mailings find a real estate company that you can approach in person, talk to an agent find out what you could do to help him, his ideas on what make a property sell better and yours maybe different. Once you get a feel for what they are looking for then you can do a mailing that would be more attractive for the masses.
A while back my parents put their home up for sale in a different state as the home set on the market the real estate company told them that he would hire a lawn care company to take care of the property, but they would have to pay for the service.
About a decade ago while I was looking for a rent house I went through a local real estate agent that managed rentals. He sent me to look at a home when I got there there was a crew of people cleaning up the place. Being from a small town my wife new one of the people, and she revealed that they were being paid 300 dollars by the real estate company to clean up after the previous renters left. I know most of us would not want to clean up the inside of a house, but that could be sub contracted and we could take our share for cleaning up the yard.
Just something to think about. Hope it helps.