Advice for Sub2 on Apartment building

I have a seller who needs some cash quick and is offering the following deal:

24 unit apartment bld.
Asking $585,000 appraises at $725,000
Seller will keep existing loan of $552,000 and offer sub2 this loan with $33,000 needed for downpayment.

I asked about a due on sale…He replied the loan has this clause but he contacted them and they responded, " very seldom would they call a loan due if paid on time."

I need advice from those experienced with sub2 as to what my risks are here if the loan is called or anything else I might need to know about as I haven’t done any sub2’s.

Thanks for input.

Mark ???