The short answer is no. It's not mandatory, but it will depend on the type of business.
- If retail, you will want a lawyer to attend to your lease agreement.
- If service based, your fee-for-service contracts.
- If a family concern, your succession plan.
- If with other people, your partnership agreement.
The list goes on, but you get the picture. Call in an expert when you need them. Alternatively, it can't hurt to discuss the business model with a lawyer before starting, if only to find out you don't need one.
If you have never ran a business then YES. Best to get the foundation right (including legals) from the beginning as it can be very costly to untangle in future if setup wrong.