Your name must be unique, and not deceptively similar, to any other trademarked name or business. It is also required that your name not be used to intentionally misrepresent the products or services you offer. For LLCs, nearly all states will also require you to add a signifier of your limited liability status, such as "LLC" or "L.L.C." to the end of your company's name. You may be able to operate under a name other than your formal LLC name by applying for and using a dba.
Individuals or startups often look for people to review their products to encourage others to buy them. You can either get started with a profile on freelancing websites or approach companies directly, offering them a review in exchange for a monetary reward by becoming an influencer. Even better, if you have your own website or blog, you could write entire posts about their products, thus allowing you to charge more money in the long run and build a portfolio with tangible results to show future clients.