Sub2 with HELOC-can I freeze it?

Looking at taking a sub2, good numbers, but owner has 2nd and 3rd that are HELOCs. iI’ve heard before that this can be problematic. Seller may nor may not realize it’s possible, but I don’t want the seller to be able to pull money back out after I’ve paid it down. Can a HELOC be frozen, perhaps by some doc I have seller sign at closing, effectively ending my worries? Mine is not a market where banks have been freezing HELOCs already.

I would ask the seller to contact the lenders to close the helocs or have the seller write a large check to you from each heloc to lock it out. Just make sure that you don’t spend it.