How do you check the legality of a new business model to make sure it will be legal, and you won't be running afoul of some law you have no idea of?
Hire a lawyer, who is licensed and trained in law and who is obligated to be honest with you and advocate for your interests, and get him/her to review your business plan. He/she will point out real or potential problems with your ideas and plans, show you legal gray areas of the law and advise you on what you can and can't do.
Some lawyers offer a free initial consultation. As an example, you can browse and read specialties and qualifications for legal help in New Jersey: https://www.justia.com/lawyers/business-law/new-jersey
There's no substitute for real legal advice; not consulting with an attorney before signing contracts or starting a business can put in in real legal jeopardy. Don't ask legal advice from randos on the Internet, as they are not trained or licensed, and it is illegal to act or work as a lawyer without being licensed.
As ohwilleke points out, you may want or need to consult several different lawyers.