The landlord tenant code is generally a state law statute. 

If there was a will then it will control who gets the house, otherwise the relevant state statute for intestate succession controls inheritance of real property, but probate will likely be required to get clear title.One strategy might be to obtain Quit Claim Deeds from the heir(s) and rent the property while waiting out the IRS lien. 

Some of the files are somewhat stale, but still within the statute of limitations for our state.

I've been through this prove it stuff before, you can begin by reading collection requirements of secured indebtedness in state stautes and then go to federal statutes, Fair Collection Practices, & the UCC.The idea is that over time a creditor abandons the claim if they fail to make an active effort to collect a debt.

Each state has a Statute of Limitations where your local municipality can take legal action against you for the un-permitted work and have you correct it according to your state's building code.

Judges frown on landlords who don't know the laws and violate statutes.

@Joan SotoHere is a link to 475http://www.leg.state.fl.us/statutes/index.cfm?

The firm application is here: https://www.ncrec.gov/Forms/Applications/FirmLicenseApp.pdfThe way NC REC rules work (as opposed to NC statutes in Chapter 93A) are spelled out in 21 NCAC 58A.0502 entitled FIRM LICENSING.

Every state, county and city or municipality has statutes, or specific laws, that govern these types of transactions.

They know the ins and outs of the statutes and the court system and will be able to give you a solid answer.Carefully document everything.