Closed on Duplex Today! Tenant repair request 4 hours later!

[Luke Marlar]

Pretty excited to have just closed on my first duplex today, and within 4 hours I receive an email for a repair request.  The repair request states that "Sink is clogged and they have tried Draino but it didn't work"  In the lease it states "Tenant is responsible for charges for unstopping plumbing and or sewer line when caused by tenant"

Any advice on how to handle this problem?  Should I schedule a plumber and let the plumber determine the cause?  Then if the cause is determined tenants fault, charge the plumbing to them?