I also have some capital to contribute.Could someone explain how syndications are typically structured, and how are people using Other People's Money (OPM) to build large portfolios with little to no money down?

This includes structural components of the building.

They are tearing it down to build a logistics facility.

I am most comfortable with long-term rentals, but I would like to try a flip or two to build my capital.

If this job popped up out of the blue, your intent was not to move within the 1st year, so you may be ok.If you are planning on building a portfolio of homes, it is safest to stick in your home for 12 months to reduce the appearance of potential fraud. 

That will allow you to build the additional legal space further amplifying the value of the proprety (more HELOC money). 

It's actually the best strategy in the Nashville area if you can build an HPR yourself and own both, STR the other side. 

You'll get a feel for the age of the neighborhoods, the vitality of the commercial buildings, the ease of location, the closeness to jobs.The markets you're describing are more linear, and usually have lower capital appreciation.

Build your team of people or as Brandon Turner from the Bigger Pockets Podcast calls it your CORE 41.

Wealth Building: Paying off the first STR focuses on cash flow and financial security, while buying another property focuses on scaling and wealth building.