Purchasing a occupied property outstanding water sewer bill

[J. Jake stone]

 Interested in purchasing a duplex occupied currently with tenants what is the best process /way to proceed 

Talk to the my real estate agent  he says there’s no information available on the tenants-what is the best way to go in this situation how do I find out how much the outstanding water bill is I see the taxes are behind about $1800 

 He advises make an offer with proof of funds subject to the inspection my question is what’s the best way to come up with that number without knowing these other variables 

Thanks