Your buyer is in compliance.  

Some people here blissfully suggest you can just hire an MLO who does not work for you to cover that issue, but in many states, that is illegal and, it does not negate your need to have the proper lending license.If you have a lending license you also have to have a compliance management system and proper record keeping.

Copeland, this topic is way above the pay grade for those who think they know what they are doing, you cannot assign a seller financed note without consent of the note holder,  you cannot put n owner occupant in the house like a lease to own without compliance with Dodd-Frank, as applicable, a contract for deed has the same issue today and many more, any lease option greater than 12 months will be determined to be a sale without special provisions being taken for the IRS......and you still have predatory lending issues regardless of how much you may "help" someone while taking their property, even if they know they are losing. 

There are several advantages to the Solo 401(k) for those who do qualify, but maintaining qualification and compliance is important.  

Make sure they invest in Real Estate too, and understand Tax Planning in addition to Tax Compliance.

The dollar value for which it is "worth it" to become an S-Corp is almost solely dependent on your costs associated with income tax filing, payroll tax compliance filing and your unemployment experience rate. 

Only the govt. portion is somewhat guaranteed if the tenant remains in compliance.

They have no obligation to ensure the compliance of a specific transaction, they just document and execute it.  

Keep track of all communications and payments in order to demonstrate your compliance with the terms -- just in case there is ever a question about that. 

They fulfill a very basic field oriented compliance function.