Most departments of real estate have a stated mission to protect the public.

After that you need to have a land use attorney establish an HOA and go through the CA Department of Real Estate for it (assuming one is needed).So as far as basic research to get started, look up the map and/or legal of the property you're interested in.

@Joe Maron Most lenders have underwriters/underwriting departments that are digging into all kinds of things.

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It also says that the negligent owner that causes the problem should pay for the reparations, and that health issues should be reported to the Allegheny County Health Department.  

(ref. http://www.decaturga.com/city-government/city-departments/administrative-services/taxes-and-fees/tax-faqs).

Tell them to pound sand and if they complain, let them take it to the housing department or a court and see if their case has merit.

@Eddie Starr  Completely agree with Greg's comment above, a local bank and their commercial lending department would be your best bet. 

@Brenda WhittakerSounds like you should do the following1) Notify the tenant of an increase in cost, if they don't agree, ask them to leave or evict them if necessary.2) Do a full inspection of the house and prepare to do some maintenance and keep up with it, I actually have a resource in this department that helps coordinate maintenance on your behalf so let me know if you want my recommendation3) Reach out to a qualified leasing agent or a property manager who does 1 time leasing, OR screen tenants by using services like Naborly that do tenant screening for you.

I would set up a meeting with someone in the community development department and ask about the parcel.