I've thought about doing this type of advertising. It's fine until you go up to someones house and they are really mean or try to throw something at you. No matter how innocent you look, it's going to happen.
Door Knob hangers are very effective because they reach a direct market. I would suggest putting on there...
We just cleaned your neighbors house and they said you might be interested in having your home cleaned as well... or something to that effect. Then they will ask the neighbor and if you did a good job, they are going to tell them.
Half of my business is repeat customers, the other half are new customers.