I worked with a guy who was doing this a couple years ago - at that time, it was extremely price competitive and I would imagine it' even more so now.
He had a backdoor renovation business that seemed to make money, but the trash outs were money losers based on labor, trash dumping, and equipment expenses and competitive pricing....these services were loss leaders in hopes of getting the foreclosure repairs or renovating foreclosures for investors.
I suggest that you pick some of the top foreclosure real estate agents and contact them in hopes of developing a relationship and getting business since they are the ones who have a stable of foreclosures and order many of the services. Most banks will not order these cleaning services directly.
Good luck in that tough, competitive environment.