You'll need to get in with a property management company, and therein lies the problem.
Same as always, if this is what you really want to get into then put yourself / company about abit, by all available means.
We clean a fair few communals, but this is at build stage. After this they are handed over and we have nothing more to do with them.
Deals are usually in place between the management company and their preferred cleaner and have been for many years so this is a hard nut to crack.
Be prepared for loads of knock-backs and a higher than usual number of rude people, from secretaries upwards, on the other end of the phone line during the preliminaries.