@Ross Benedict
An LLC is not NEEDED in order to start your REI business, but it's a good idea to consider it. It really comes down to your level of comfort regarding potential liability and the extent of assets that are at risk,
An LLC is intended to encapsulate your property within a separate legal entity for liability purposes. In other words, you keep your personal and business assets separate so that if your business incurs a liability (for example, a judgment against you in a personal injury lawsuit arising from a claim that an unsafe condition at your property caused the injury), your personal assets are insulated from being liquidated to satisfy this judgment.
Many RE investors keep each house in a separate LLC. The reason for that is the same. The idea is that assets (houses) in separate LLCs cannot be reached to satisfy a judgment attached to a particular LLC.
The concept is great. In reality, you need to be aware that you can certainly conduct business in a way that could negate the advantages of the LLC (e.g., comingling (mixing) personal and business funds). This is called "piercing the corporate veil" and allows a plaintiff in a lawsuit to go after you personally for liabilities incurred against your business. So, it's imperative that you properly follow the rules relating to operating your business.
Also, it can be a headache to manage several different LLCs covering several different properties. Similarly, the costs for LLCs in certain jurisdictions can really eat into the bottom line. The tax laws of a particular jurisdiction can do the same. So you really need to have the proper guidance to get the most from the LLC structure. Like anything in business, it can be complicated, but you CAN learn and understand it.
Another (not exclusive, but potentially supplemental) way you can limit the risk is to get an umbrella insurance policy on your properties that will protect you by paying out for covered liabilities in the event your property incurs them. I highly recommend an umbrella policy on any property. They typically aren't that expensive for basic coverage, and will probably be sufficient for the most typical claims you might encounter. That said, there are exclusions, and you need to read the policy to understand what is covered, to what extent, and what isn't.
For ME, at a minimum, I have a separate LLC that runs and manages my business and separates business assets from personal assets. For multiple properties, I'm of the opinion that there is a threshold dollar amount of assets I will risk in each LLC. So, each LLC may hold e.g., ~$250,000K in property (could be one property, could be multiple properties) and each property therein will have an umbrella insurance policy.
Long story short, it depends on how and whether you want to distribute the risk and then how that plays against the complexity of managing multiple LLCs. There are a lot of variables, but you can ultimately figure out the best way to go for you with help from a good attorney and accountant.
For those starting out in buy and hold, I recommend that you at least have a separate LLC for your business, even if you don't have more than a single property. It MAY be overkill, but I know I don't want to be that guy posting on here about how I relied on only an umbrella policy and ended up losing all of my personal and business assets because of a freak accident or savvy plaintiff.