They are going to give you a couple additional sentences to put into your lease stating that they will pay directly and can be the ones extending but what they wanted seemed to make sense so I had no issues amending it. 

The Code was amended early on in response to complaints from people who already were in that business. 

Who knows, maybe the tenant wants to make amends and is willing to do whatever it takes to stay. 

You want them to file 2 years of returns, to multiple states, and with specific tax issues...that will likely need to amend all of your old returns?

First, many states Real Estate Commissions have promulgated contract documents such as Purchase Contracts and amendments, Listing Agreements, Disclosure Notices, and many others.  

If your lease doesn't have a no smoking clause, you should consider amending it at renewal time, if you decide to keep them.

It doesn't sound right the amount of taxes that you paid on your STR over the past couple of years.I would have a CPA review your past couple years worth of returns and see if there was any errors made which may require an amendment.

This adjustment is reported on IRS Form 3115 and does not require amending any prior year tax returns

If you have a solid level of income, you can always amend. 

My lease also contains the following:"In the event that the premises are located within a community with a condo or homeowner’s association the Tenant and the Tenant’s guests, employees, family members and other invitees of the Tenant shall comply with all association rules, regulations, and requirements.Landlord hereby notifies that the Premises are located within the <condo name> Condo/Homeowner’s Association and that this Lease, the Landlord and Tenant, Tenants’ guests, agents, employees, visitors or family are subject to all terms, conditions, provisions, restrictions and rules as the now exist or may be adopted, modified or amended by the governing Association.