To start a business in Illinois, you should consider following these legal steps:

1. Choose a business structure: The first step in starting a business in Illinois is to choose a business structure. The most common forms of business structures in Illinois are sole proprietorships, partnerships, limited liability companies, and corporations. Each structure has its own advantages and disadvantages, so it is important to choose the one that best fits your needs.
2. Register your business: All businesses in Illinois must be registered with the Illinois Secretary of State. This includes obtaining a tax identification number and a business license.
3. Obtain necessary permits and licenses: Depending on the nature of your business, you may need to obtain additional permits and licenses, such as a food service or liquor license. It is important to research and obtain all necessary permits and licenses before starting your business.
4. Obtain insurance: Depending on the nature of your business, you may need to obtain liability insurance, workers' compensation insurance, or other types of insurance to protect your business and its assets.
5. Comply with tax requirements: All businesses in Illinois must comply with state and federal tax requirements. This includes registering for state and federal taxes and obtaining necessary tax permits.
6. Protect your intellectual property: If your business involves creating or developing intellectual property, such as trademarks, patents, or copyrights, it is important to protect your intellectual property rights by filing appropriate applications or registrations with the appropriate authorities.
7. Create legal agreements: As you start your business, it is important to create legal agreements such as contracts, leases, and employment agreements. These agreements should be drafted by a licensed attorney to ensure that they are legally enforceable and protect your business interests.

It is important to note that these steps are general guidelines and there may be additional legal steps or requirements depending on the nature of your business. It is always recommended to consult with a licensed attorney to ensure that you are complying with all legal requirements and protecting your business interests.