Like @Brian Adams, I believe QBs is a good solution.  

Identify their problem/ needs, and show them why you are their best solution. 

Remember you are a solution to their problem - problem being a house they need to sell, but can't sell through a traditional agent.

That's is a sustainable business game plan right there.

The Code Solution is solid

For a turnkey kind of solution it can be very very costly.We have recently been going through the most aggressive rehab project to date (residential rehab) and I've had to learn about masonry a lot more. 

An astute tenant sometimes tries to take advantage of a less knowledgable owner to put things in their favor.If a tenant is really struggling then the owner has to try and meet in the middle for solutions that work for both parties.No legal advice given.      

the in control person :) should to be happy to help you because they may have to bear the brundt of it ALL.Try to get a solution who is irritated and offer them to move with no penalty and good report to next landlord. then if that doesnt look like it will work: Say you know I have to say I would like all of you to leave if you are not happy.Here's your notice to move-60 days----Peace out orEvict THAT PERSON AND all of any unknown tenants altogether, As Unknown Tenants.Settle by them all signing a master lease FOR THE WHOLE RENT all tenants responsible as a SECURITY DEPOSIT with respective amounts also individually agreed.Take the girl issue with her alone in the house what did she pay--what portion...offer in court to the judge. after you have filed the eviction on all of them.

Parents shall not lease property and leave children under the age of 21 by themselves overnight.RISK OF LOSS AND INDEMNIFICATIONGuest agrees that all personal property, furnishings, personal affects and other items brought into the Property by Guest or their permitted guests and visitors shall be at the sole risk of Guest with regard to any theft, damage, destruction or other loss and Rental Agent shall not be responsible or liable for any reason whatsoever.Guest hereby covenants and agrees to indemnify and hold harmless Rental Agent and their agents, owners, successors, employees and contractors from and against any costs, damages, liabilities, claims, legal fees and other actions for any damages, costs, attorney’s fees incurred by Guest, permitted guests, visitors or agents, representatives or successors of Guest due to any claims relating to destruction of property or injury to persons or loss of life sustained by Guest or family and visitors of Guest in or about the Property and Guest expressly agrees to save and hold Rental Agent harmless in all such cases.RELEASEGuest hereby waives and releases any claims against Rental Agent, the Property owner and their successors, assigns, employees or representatives, officially or otherwise, for any injuries or death that may be sustained by Guest on or near or adjacent to the Property, including any common facilities, activities or amenities.Guest agrees to use any such facilities or amenities entirely at the Guest’s own initiative, risk and responsibility.ENTRY AND INSPECTIONRental Agent reserves the right to enter the Property at reasonable times and with reasonable advance notice for the purposes of inspecting the Property or showing the Property to prospective purchasers, renters or other authorized persons.If Rental Agent has a reasonable belief that there is imminent danger to any person or property, Rental Agent may enter the Property without advance notice.UNAVAILABILITY OF PROPERTYIn the event the Property is not available for use during the Rental Term due to reasons, events or circumstances beyond the control of Rental Agent, Rental Agent will immediately return all payments made by the Guest, whereupon this Agreement shall be terminated and Guest and Rental Agent shall have no further obligations or liabilities in any manner pertaining to this Agreement.ADDITIONAL TERMS TO THE RENAL AGREEMENTIn addition to the standard terms included herein, Guest acknowledges and agrees that the following additional terms and conditions apply to the Guest’s rental of the Property:GENERAL PROVISIONSThis Agreement contains the entire agreement between the parties with regard to the rental of the Property, and any changes, amendments or modifications hereof shall be void unless the same are in writing and signed by both the Guest and the Rental Agent.This Agreement shall be governed by the laws of the State of New York.The words “Rental Agent” and “Guest” shall include their respective heirs, successors, representatives.The waiver or failure to enforce any breach or provision of this Agreement shall not be considered a waiver of that or any other provision in any subsequent breach thereof.If any provision herein is held invalid, the remainder of the Agreement shall not be affected.Any notice required to be given under this Agreement shall be in writing and sent to the contact information included herein.This Agreement may be signed in one or more counterparts, each of which is an original, but taken together constitute one in the same instrument.Execution of a digital signature shall be deemed a valid signature.Security - There is currently an outdoor security camera to protect home during periods property is empty.Pets – provisional with approval and pet feeGuest is responsible for cleaning up any/all pet refuse.

Well explained example Charlie MacPherson, and great solution suggestion at the end.