I think it is a great idea as well. I work in swimming pool service, and you would be surprised how many people (and hotels) want weekly service just so they don't have to spend time (or unqualified employees time) dealing with the maintenance.
Where do you live? I would believe this opportunity would work better in a large city where there would be more chances someone would be interested. I would make sure you draw up a contract outlining what will be done and when, and definitely assume some liability to give the customers security.
Getting ahold of a mailing list may be pretty difficult, so you may want to think of how to get the word out.