Closing is the easy part. The ninety days after it decide whether you bought a business or a set of problems, and the most common way to damage something you just paid for is to improve it immediately.

What you actually bought is a set of relationships: customers who stay, staff who know how it works, suppliers who extend terms. None of those transferred with the paperwork. They transfer over the first three months, or they do not.

Have the transition agreed in writing with the seller before closing: how long they stay, doing what, how they will be introduced, and how they will be paid for it. A handover arranged after the money has moved is a handover you are asking for as a favour.

Make a list of everything that has to change hands and work out which items take weeks rather than days. Licences, insurance, merchant accounts and utilities are the slow ones and they are easy to leave until they stop you trading.