@Serena HeCongrats on getting licensed! I am in NYC and I know there are some variations from state to state but these core principals should be the same for all states. You do need to have your agent (salesperson) license with a broker to legally conduct business as an agent within your state.
In order for you to have access to MLS you would need to be signed up with the local MLS which can only be done through a broker and not to an individual agent. It is frowned upon by all MLS companies to give your login to others to access your account (with the exception of an assistant). The fees for the MLS do vary depending on MLS company.
I started out on the realtor side of the business for many of the reasons you stated. I got my license more for protection when moving deals to investors since I am in the extremely competitive market of NYC. So I would explore moving your license to a broker for protection but it will not really give you a competitive advantage in finding deals on MLS.
I hope this info helps! Keep us updated on how things go!