Buying rental property - Can existing leases be modified?

[William Hirsch]

Hi, this is something that I can't seem to find much information on, and perhaps someone here can help.

If you buy a rental property with current tenants under active lease, can you as new owner break/amend the lease and set up a new/amended contract? 

I suppose you have to honor their lease unless there is enough basis to break it, but I'd like to find more information on this.

My concern is that existing lease may not be thorough enough, and may be excluding

important clauses such as whether a landlord pays any utilities.

Thanks in Advance !