When contacting some of these firms ask for referrals of other property owners who have a similar situation to yours and find out the good the bad and the ugly.
In any event you do need to find out what all the laws are relating to rentals even though the rental company should adhere to them. To that end you might want to check these links
LANDLORD TENANT ACT: http://jecclassroom.unm.edu/landlord_tenant/ pamphlet
Best of luck