You have to understand that you will lose the value of the home over time which is the biggest drawback.

Major drawback, if LLC is primary borrower and student is sole member, might get beat up by commercial lender on rate/terms. 

As long as the potential buyer is uninformed about their drawbacks, he/she won't use them as a negotiating tool to hammer you on the home price.

What I meant to ask is are their any drawbacks in a SDIRA VS a standard IRA?

I think my biggest draw back right now is where do I start in regards to finding a seller that's motivated.

Does anyone see purchasing the duplex at full value instead of at the suggested 10%-20% discount a big draw back? 

While using your HELOC to make the down payment on a secondary home sounds like a great idea, there are some drawbacks you should be aware of.

This is not to say that you will never run into issues with a PM companyManaging your own properties does come with its drawbacks, but in my experience it is definitely doable and with the right tools to help you manage, you can save a lot of money over time.

Curious if anyone has tried that or sees any drawbacks to it?

The stress of juggling my day job (in Commercial RE) while building to critical mass would be trying, and essentially "selling" myself and my services for a period of time are the obvious drawbacks.