Removing old tenants before a buy+rehab

[Ben Hollingsworth]

We're about to start buying small multi-family rentals, preferably those that need some rehab to boost rents.  If the building we buy is already full, how do we get rid of the old renters so that we can rehab the units and then refinance to get our money back?  For example, assume the old renters are paying $300/mo, and we expect to get $600/mo after rehab.

Do we have to officially evict everyone?  Do we have to wait til their current leases expire & then not renew?  Can we raise the rents immediately after purchase, regardless of their old leases, and then wait til they move on their own?  What do the rest of you do?