What is the best way to structure the partnership?

House hacking is the BEST way to get into real estate investing and that's how I personally got started as well too.

Also, if there’s a mortgage, transferring it to an LLC could trigger the due-on-sale clause, requiring lender approval.Better Alternatives to Avoid Reassessment & Save on Taxes:Living Trust (Best Option) – Your aunt and stepfather could quitclaim their interests to your aunt, who then sets up a revocable trust naming your mother and you as beneficiaries.

You're likely best off wholesaling the property and using those funds to invest in the deal or invest in something else.

All the best.

What are y’all‘s favorite BP episodes on house hacking? especially for beginners? (i.e. a college student with a huge passion for real estate and financial freedom)

Interviewing multiple GC's is the best way to operate, but make sure you are communicating to them that you may want to limit their scope of work as you may intend to SUB out some of the work ourself. 

Find little ways sacrifice. 

I've read numerous guides and watched many YouTube videos, so I have a good theoretical understanding, but I'm still unsure about the best way to start investing in U.S. real estate.My plan is to begin with long-term rental properties and then eventually move into flipping and the BRRR (Buy, Rehab, Rent, Refinance, Repeat) strategy.

That's probably your best bet.