You need to get advice from a competent employment solicitor before you go ahead. The laws on this are quite complex and can be demanding on the new owner of the business. For example, if you make any of the staff you take over redundant you would probably be liable for their redundancy pay for the whole of their service with the previous employer (or even the one before that if the business has changed hands before). Also, you might have a problem if you want to change the terms in their contracts for the worse.