If there is an existing lease, the lease transfers to the new owners, who have the same obligation to the tenants as the former owner for the duration of the lease.  The new owners have the option of offering to "buy out" the existing tenants from the remainder of their lease, but the tenants have a right to stay until their lease is up.

A no-cause eviction is simply refusing to renew the lease once it is up.  You can't evict someone in the middle of their lease except for cause, and that is an extremely limited set of circumstances proscribed by law (non-payment of rent, etc.).