While less than 10% of the mortgage industry offers 40-year mortgages, here's something to factor in: they often come in with a rate increase of 20-35 bps.Assume 35 bps.$300k mortgage at 7.25% (30-year): $2,046$300k mortgage at 7.6% (40-year): $1,996Technically, it lowers the monthly, but not by much once factoring in the rate adjustment.

I currently work as a Pipefitter (think plumbing but on industrial steroids).

As a licensed Real Estate Broker in Maine, I managed the acquisition and renovation of 1272 Lakins Rd, Etna, leveraging my expertise and industry knowledge.

I am not an expert here but my thought is that you would learn a lot by getting your license and have more credibility in the industry at large so if your time and finances allow- get that license:)

If you decide to revisit STRs, you might want to explore properties where you can project expenses independently, such as using local STR forums or online tools to estimate maintenance, management, and occupancy costs.For networking and strategy-building, you might find local meetups or groups beneficial.

Its a lot of money to put into someone who's new to their life or the industry.

Then I begin to research the industry.

I don't disagree that Airbnb claims can be difficult but this is all very common in the industry. 

You will lose one of the best benefits of the real estate industry, appreciation.

What rate, term and amount borrowed did you get for the ADU build and what was the cost?