@Vicki K.
Good question on the holding company. Several reasons in my situation.
1) @Jonathan Twombly pointed out, it's another layer of legal protection. My property LLC is not owned by me, it's owned by the Holding Co. LLC. It creates another hurdle for when you do get sued.
2) Streamline tax filing. My property LLCs (like many single member ones) are considered disregarded entities. They just pass through to the Holding Company for tax purposes.
3) Streamline finances. Holding Co. can charge the property LLCs a "management fee" and then deploy that cash elsewhere. Instead of the property LLC cutting me a check, it pays the Holding Co. Holding Co can then do what it wants to do with the cash. Buy a new property, invest in notes, or even purchase a non related real estate business or assets and still have legal productions built in.
You're very wise to keep your management company separate from your properties. That's a case where you could form a holding company to keep them all under one roof. Both management company and property companies. That said, ALWAYS consult your own tax and legal advisors. Everyone's situation is different.
Hope that answers your questions and is helpful.