How would you handle this tough landlording scenario?

[Rick Baggenstoss]

I just purchased a house as a part of a package.  The bad house has a bad tenant with no lease, she's impossible to reach, and a ton of people are living in the house.  The house is in disrepair too.  I don't have keys to the house either.

Water is in seller's name, so that should be shut off soon.  Without a lease, she can't get it turned back on.

I've been calling daily and have stopped by a couple of times.  Today, I left my card with her oldest daughter (adult).  

I only have the word of the seller as to the rent amount of $600 -- $200 a month below market.  

House is in a tough part of town so a vacancy could become pretty expensive, but I'm happy to risk it.

My next step was to start the eviction process as a catalyst for getting the conversation going since I can't seem to get a return phone call or catch her at home.  At some point, I'll pay cash for keys rather than duke it out in court without history or a lease.

What would you do?