Signed a 14 mo lease. Told 6 months later I need to reapply

[Matt Larson]

I signed a lease for a 2 bed 2 bath apartment in Denver, CO.  6 months ago in November.  I qualified financially myself for the 2/2.  I told them about my plans to get a roommate when I applied.  They said since I qualified financially, it is not necessary  for future roommates to qualify financially but would need to pass a criminal background check.  I then got a roommate for the second bed room.  She stayed for 5 months.  

     I recently had to find a new room mate.  After she was approved I was told I would need to reapply.  They said they changed the policy since I signed my lease and the new policy is that if any roommate moves out and a replacement is needed all the people in the apartment need to reapply.

    I told them I will not be doing that because that's not how contracts work.  One party can't change the terms of the contract during the contract.  They did back down, but it made me think.  If it happened to be in the lease when I applied is that even legal?  Can they make you reapply during a lease?  How common is this?  Would they have to state this during the application? 

 If I happened to get arrested for DWI or something during that time can an apartment complex kick you out? IF they kick you out can an eviction go on your record?  How many days warning would they need to give you?