Keep an eye out for small landscape companies selling there business because it isn't worth much. You will probably end up giving it away in your eyes if you are smaller.
I remember one guy used to post "cost of equipment and a case of beer" which is surely over simplified, but makes a point.
It doesn't matter if they have a contract or not. Despite the fact that it probably will not be valid under new ownership, are you really going to spend the money and time taking someone to court over 100/month.
Can the new owner run the biz from a computer or does he have to load the trailer each morning and wipe his employee's asses?
One way you make your accounts more profitable is working on site with the new owner for a while. This allows better retention rates.