Our lender has informed us that we need 12 months of rental history to use the actual rent for financing purposes, or we must rely on the appraiser's fair market short term rental value.

Lots of loan options can close in an LLC, helocs usually need to close in your personal name.

With the duplex, you can do both rental options.  

These are very different than Subject-To, as the loan actually transfers to your son's name, and off the seller's name. 

If you ever need guidance on financing options for flips, rentals, or new construction, I’d be happy to help.

The reason why I ask is because that could determine what loan options are available to you (and interest rates). 

If you're considering purchasing under a business name, consult a CPA or attorney for setup and financing options.

I would be very careful with a lot of course or guru in general right especially a price tag like that what I would always recommend reading the contract and see who is the person more in favor and if its not you then dont sign up very rare to see someone actually benefit from a course.

I actually had your underlying question in mind.  

If everything checks out, they could be a solid option for your first investment deal.