i see two options here 1) you can go back to dad and break it down as hey i cant close on the house until it's vacant and see if he can help in getting them out, 2) offer some moving expense if the lot is really that desirable to you I know not what you want to hear as the investor but it has worked on numerous occasions, 3) you will have to take it to the courts as final resolution so the sheriff can remove them. Hope it works out :)
@Zimean Vickers I hear you, sometime people just cant help it but you have to remember your running a business too and can't let those things affect the plan
Why not Just request a price concession from the seller for the cost of the eviction?
It is amazing what some people can live like. Assuming dad has at least acquiesced to the sons' occupying, they may legally be his "guests" not his tenants. It seems to me that until you own the property the sons have no real motivation to move. Having the place declared uninhabitable usually works to the advantage of a tenant anyway, and may require the landlord (eventually you) to make repairs to make it habitable (although a tenant's recourse is typically withholding of rent, so ...).
In the absence of formal or informal lease terms (and considering the lack of rent), the sons are probably not tenants and thus eviction may be an inappropriate solution. However, in that case consider the elements of criminal trespass. See North Carolina's first degree trespass and second degree trespass laws. A financial incentive to move may be less messy though. (Don't give $, or at least not all offered, until they're gone.) Look for win-win where possible.
Police removal of trespassers, if necessary, can often be accomplished far more swiftly than an eviction, but may still require substantial verifiable evidence of ownership (e.g., legal deed, etc.) and absence of a lease (e.g., shown in affidavit/statement from former owner-dad). Talk to the police about what they'd want to see.
DISCLAIMER: The above is provided only for informational/educational purposes, and does not constitute legal advice. You should not rely solely on this information as the laws and procedures in your jurisdiction may materially differ. You should consult a local attorney familiar with laws and processes of your jurisdiction and the details of your situation which may significantly affect circumstances and outcomes.
@Zimean Vickers It would be worth finding out what evictions are like in NC. If it's relatively easy, and something you can deal with, then get the process started ASAP.
@Jill F. Called it exactly right - if you move forward with closing, do a hold-back of the amount of funds required for evictions. Make sure you include all costs - sheriffs, movers, storage, etc.
Normally I'd want to know a lot more about the basement flooding, but since you've said it's a demo, I'd let it go and address it with drainage and/or french drains when you rebuild.
I agree with @Victor N. Call code enforcement. They'll deem in uninhabitable and the sons will be forced to move out. Much easier than an eviction. But yes, make sure you won't incur any fines.
Oh wow! You all are awesome- Thank you so much for all your help. This information is priceless and greatly appreciated. I feel like I have the support of a community with a wealth of information to help with the success in my journey...
I'm getting started this morning to seek all the options you guys listed- advantages and disadvantages. I will keep you posted...I hope you all have a day of success. Thanks