1) Apartment Complexes.... The Management Company needs to clean the appartments before renting them again.
Also, They are often a source of "preferred providers" when a tennant needs a service.. See if they'll put your business cards in their lobby
2) Develop a relationship with Real Estate Agents. Especially the ones who represent sellers, as opposed to buyers. A sellers agent is going to make the house they are selling as marketable as possible, and they will often make their clients get their homes professionally cleaned before showing it.
A Great Resource would be to join a BNI Chapter. (Business Networking International) But you'll want to do this once it's your full time job... They don't take part timers. Learn more at
www.bni.com