My parents have a beautiful cabin in big bear that they never use and I have finally convinced them to turn it into a vacation rental.

My parents also share that opinion.

My parents recently purchased a duplex of their own and I've been looking for a multifamily house primarily in towns in Central NJ (Union County). 

Then the best case scenario is that your girlfriend is donating $10,000 to a charity case. 

Is it worth setting up a parent LLC for my companies or keeping them all separate?

@Jeff Brower @Derek TellierI'm just a recent grad still living with my parents for free since i don't need to pay rent.

But I want to thank the academy,  my parents, and all the silly lil investors that did so much hard work putting up YOUR bandit signs, and spent so much money on DMM so we can get your leads...Thank you.

The only thing that you could consider "donated" is the advice and time of the hosts.

Both of these structures offer the "parent" Series/Trust which can hold an infinite number of "child" series/trusts, so it would allow for the future investments when they approach.

Would anyone know if I need to setup a separate EIN number for the parent and each of the series under it or just have an EIN for each of the series companies only ?