Hi Bob, welcome aboard
I used to work in the hotel business and wanted to share how they went about it. Its really how most businesses do, if they do, i suspect. Working at the front desk of the hotel, each night a person is assigned to call around and get the rates for the evening at a list of other competitive hotels. They also ask the occupancy. A log is created and monitored over time. Other hotels provide the information and collect it similarly. Over time, believe it or not ... this is done openly and with agreement. All of them do it.
In your situation, I think it is just as simple although you don't need to openly identify yourself or your intentions. For example, pick up the local yellow pages and start by listing out all of the companies. Now call them all and ask your questions just as a customer would. Take detailed notes. Prices, services, other stuff mentioned. Then line up your lists and see what your potential competition is charging (or quoting in your case).
Regarding finding other businesses for sale, I've got to say the same aproach is probably the best route. Anyone have a similar business in your area? Pickup the phone and call them and see if they have any interest in selling. This can work occassionally. Tell them, if not, to give you a shout if they ever are in the future - you would like to be able to consider it.
Regarding buying a biz, i'm not sure I would go that route unless it made a whole lot of sense. An existing client base may.
One potential type of lead might be apartment complexes in your area who need their general areas and offices cleaned.
One other tip regarding calling around, if you are concerned about being identified then call one city away from your market. For example, if you are in houston then call other similar companies in Dallas.