Great question Phillip and one that anyone just starting out should be asking!
There are a number of advantages to forming great working relationship with a Realtor a priority moving forward. One that you will hear often is access to the Multiple Listing Service (MLS) which enables an agent to send you properties that have been listed on the market within your search criteria. The MLS also enables a Realtor to run accurate comparables for properties that have sold recently, allowing you to price investment properties accordingly.
Outside of the MLS a Realtor is your key to view homes legally and ethically in your area, as often times there are certain times or restrictions placed on unlicensed folks for showings. A Realtor who is active in their market and areas should know things from demographics to price points to market appreciation and other valuable information, and if they do not off of the top of their heads, they can easily access that information or find someone right away in their network who does.
That is briefly some of the highlights of what advantages there are, but keep and mind that there are more and others can jump in and add to this start.
The only perceived disadvantage that comes to mind (I may be overlooking something as I am biased as a Realtor here in CA) is the cost associated with working with one. This is cost is accounted for during the close of the sale at an average rate of 6% commission (negotiable) and if an agent is providing all the resources that they should, that money should be well worth it. Note that not all agents are equal because some are not trained or proactive in their education and/or ethics, so screening may be another thing to consider (essential if you ask me) to find someone who specializes and is successful in the type of real estate you are looking for and in the area. For example as an Realtor myself, I wouldn't claim to know all of San Diego, let alone all of CA, even though I am licensed here and have lived and worked in San Diego since I can remember.
Hope this helps! Feel free to post here or reach out with a personal message if you have more questions.