[Oakland, CA] Tenants in Unit But No Lease Agreement

[Calvin Kwan]

Hey Guys,

I came across a duplex in Oakland that may be a great opportunity for my first investment property.  It's a duplex that currently has an occupied and  vacant unit.  The occupied unit doesn't have a lease agreement in place with its existing tenants.  The owners are absent, so they haven't been actively managing the property, and they actually don't know what's going on or who's living in the unit.  

Ideally, I'd like to get the property vacant so I can reno both units and rent it out at market.  With the occupied unit, what's the best strategy here?  How would I go about establishing who has legal tenancy if there's no record of a lease?  Do I just have to get the tenant/s to start a new lease with me once I take over the duplex?

Thanks for any guidance!