At this point I feel that even a high yield savings would have been a better vehicle.

Clearing or Using Land That Isn’t TheirsSome tenants start clearing brush, grazing animals, or even parking vehicles on land that technically isn’t theirs, especially if there's no fence or obvious boundary.Why it matters: This kind of “use” can seem harmless but might escalate over time.

When you see 15%+ IRR and you're doing nothing but putting in capital, this should indicate that this is a risky investment. the other factor to consider is that private placement offers have significantly less regulation than other investment vehicles, so your odds of losing your entire investment increases.

It's like an auto dealer promoting when they sell you a vehicle, it will come with tires on it, lol.

I self manage very simple 3 fund portfolio AA of TSM index funds, RE and small amount of cash type vehicles so I don’t need much but I do use a guy every few years on a fee for service basis as a check-in to ensure I’m not missing anything.

The new funds are being invested in a separate preferred equity vehicle, but the benefits would flow to the entire original investment.My key question: Does using retirement funds (solo 401K or Roth SDIRA) to support a deal where my personal trust also holds equity create a prohibited transaction under IRS rules, even if the entities are technically investing in different vehicles?

I don’t know the vehicle-per-day traffic counts (in Texas I’d check TX DOT, you might check Vermont’s equivalent), but there could be potential for more density or alternative low-impact commercial uses that don’t rely on heavy traffic.

Take the excess money you would pay in principal & put it into a vehicle that would yield you 7.5% or greater...If you find another RE deal at a 10% cap rate , interest only can be a good thing, it frees up more cashflow to reinvest in better ROI vehicles. 

However she regularly uses my maintenance staff on my unit and occasionally on other units (she recently used them for a few days to furnish a new STR including transporting the furniture - I also believe she under paid them as she paid their usual rate but they provided a trailer and vehicle to get the furniture).    

For most people, a W2 and savings plan are the first vehicles.