There are legal ways to screen for older tenants without discriminating.

I am trying to understand from a legal standpoint, where does a roommate scenario end and an ADU scenario begin?

i understand it was supposed to be done for the price you bought it at ( any legal recourse ?)

There is a 4 unit rental property in Taunton MA that I'm considering but after a little due diligence I found out that it was a legal nonconforming property.

There is a legal concept known as the fraud spectrum that accounts for liabilities that can arise out of our words and actions.

@Serges Lemo,Though I am not an attorney, I am pretty sure any lease extension you create and execute on behalf of the prior landlord/owner, would not be legal. 

Double closings without disclosing what you are doing is not legal in CA,(maybe I'm wrong) a majority of wholesalers out here will assign contracts using their LLC and/ or assignee, for that you can use any title company you want. 

It you communicate your rental criteria to prospective tenants in advance before accepting an application and application fee (required in Washington State), you would not run into this problem.It's perfectly fine to reject an application or approve it with conditions based on legal rental criteria.You may want to use a standard form, such as an "Adverse Action Notice".Here's some information from the one we use:----------ADVERSE ACTION NOTICEApplicant name ____________Applicant mailing address ___________This notice is to inform you that your application to rent the property located at ______________  has been:[] Rejected[] Approved with conditions:[] Residency requires an increased monthly rent of $_____[] Residency requires increased [] fee or [] deposit of $ _____[] Residency requires last month’s rent[] Residency requires a qualified guarantor[] Other requirementAdverse action on your application was based on one or more of the following:[] Information contained in a consumer credit report *[] The consumer credit report did not contain sufficient information *[] Information received in a criminal record[] Information received in a civil record[] Information received from references[] Information received from previous rental history or reference[] Information received from employment verification[] Inaccurate, false, or misleading statements or missing critical information on the application*If you were rejected based on a consumer credit report, you can request a copy of your credit report for free from the below-checked agency.[] Experian[] Equifax[] TransunionDated this day of ________.Agent/Owner Signature _________

Is this legal for me to have to pay all of these costs when neither I nor the person living in my unit caused this problem.

Many members are experts in their respective fields related to real estate investing, whether that is real estate brokerage, wholesaling, flipping, buy and hold, lending, self-directed IRA and Solo 401k investing, or tax and legal guidance.The site has quite a few tools that can be helpful for new members.