I would like to build several (2 - 6) "shipping container" type homes for either short, mid or long term rental.

To put this in terms, that's making yourself a "Quantum Real Estate Investor".

Just be willing and prepared to make it a long-term investment to get you mentally and financially through any bumps in the market going forward.Good luck! 

For short-term and mid-term strategies working there, the simple answer is that it depends. 

From my experience working with over 400 investors, starting early gives you a huge advantage in building long-term wealth.

Real estate investing can be an effective way to build long-term wealth, and among the various strategies, one has gained significant popularity over the years: BRRRR.

Some/many lenders don't like a 2nd mortgage behind their first (like the skin in the game), however there are both bridge or permanent financing options out there allowing you to leverage anywhere from 90% CLTV - 100% CLTV, but don't expect good terms...

You can shift your perspective to enjoy what you're doing, yet reap the long term rewards by planting the seeds today. 

That's why mature investors with long positions like Boston while places like Brockton and Holyoke are more affordable.

Then there’s city regulations—some places heavily restrict short-term rentals, so you’ve got to check the rules.If you find the right spot and automate stuff (guest communication, cleaning, etc.), it can be profitable.