Sell/split off business units from PS instance

We are in process of finalizing a deal to sell off a large portion of our business. With the sale, we need to create a separate database instance so they can continue to process transactions separate from our company. Does anyone have any experience with this? We are trying to figure out how we will purge all the data related to business units the new company is not buying from their separate instance. Any advice/assistance is greatly appreciated!
Thanks,
Alicia Kinsey