Now, there are two meanings to mngt company .One is the company that manages the whole block or estate -and you've no choice to use them -they're part of the contract.
But you mean a company to specifically look after your apartment - deal with tenants , with complaints, collect money, repairs etc. In which case I strongly endorse Bronte's comments.
Some companies charge 10% of the gross rent to do -well, frankly, very little.
(that's seperate from a letting fee where they find suitable tenants after supposedly vetting them . What's worse - if the tenants leave after a few months some letting agent will charge again).
If you set up a d.d. or s.o. with the tenat ,get a months deposit and if your apt is in good condition with electrics and plumbing thouroughly checked and appliances are in good condition then do as Bronte suggests - get a relative or firend as a contact number. They may be bothered 2-4 times a year. Or never.
If,however, you really want a mngt agent then bargain and make sure it is long established,preferably a member of some auctioneers association. Doesn't mean that much, but better than some small office just opened with a couple of idiots charging a fortune.
Oh, last thing. A mngt agency will advise you they got a plumber,electrician or whoever to "fix" a problem in your apt . You'll find the charge is much higher than if a trusted relative or frIend got hold of one.