Door entry systems for multi-family housing?

[Mike Curadossi]

Hello,

I just purchased a 11 unit rooming house and was looking to get away from the keyed entry for the main doors to get in and out of the property.  There are 4 doors total.

I am just nervous that current tenants could make copies of keys without me knowing and give them to friends/relatives/ boyfriends/ girlfriends etc.  I plan to have security cameras around the property but I will really only check them if I hear of an issue.  I also want to be able to either collect the only key they have and/or be able to de-activate their key if they were to "lose it" or when they move out.  I think this will make the tenants there feel more safe too. 

Anyone currently use anything they like and that is reliable?  I will have an on site manager but I don't want them to have to be making a new card or something every couple of days because the bar code got smudged or something. 

Thanks!

Mike