Hi my home was inspected today and on the report it says that under my bathroom sink is a thick black hose attached to the pvc it was like that when I bought my home. The buyer is wanting it to be different do I have to change it is a code that it has to all be pvc or are they just trying to get what they want not what is code. Please help me answer this question asap thank you. :)

Not knowing your local codes I can't answer that, however, if the lavatory is trapped and vented this sounds like a Fernco Coupling that connects the tail of the trap to the stubout coming out of the wall. If this is the case there's nothing in my Standard Plumbing Code Book that prohibits this. If it's been working for years I can see no reason to change it outside of looks. Good luck, Tom