Is this really a good deal?

[Lovorn Brown]

I found a 4-plex, seller asking $140K; currently has renters, and monthly rent is $2600. Landlord is paying water and sewage. Taxes last year were ~$1800, and I'm hoping to find insurance for $3000 or less. Taking 5% for vacancy, CapEx, and repairs, plus 10% for property management, using the bigger pocket calculator shows cash flow as about $700. The house was built in 1956, not in the greatest neighborhood, and probably doesn't have great appreciation potential. That's it, is this really a good deal?