I've been using "Subject To" and other various creative techniques for thirty years and I've learned a few things along the way that may make it easier and less risky if you are trying to use them yourself.
1) First,...

If you make a prohibited transaction your SDIRA SD401K is assumed to immediately liquidate, with all related tax consequences.

They are choosing to trade in that lower mortgage rate to move to a desired location, or change jobs, or get divorced, or because they have finally saved up enough for a home, or whatever else life throws at ya…So when you see the “doomer” posts online, including by reputable/popular sources, spoon a lump of skepticism into your coffee, take a sip, and dig a little deeper.

Of course people will be upside down when they trade it in or sell (they SHOULD know this, yet they will still overpay for a depreciating piece of property).

Lead with a simple credibility stack: be clear about your buy box and pricing logic, share a one‑page deal sheet on every trade (collateral, payor history, servicer notes, exit plan), and match your promises to your updates.

The questions rellay is how much of these trades can he replace. 20% or 80%?

I am an electrician by trade for 34+ years. 

You want an accountant who can help you strategize and who is responsive when you want to know the consequences of the financial decisions you are making throughout the year.Good luck.

I’m an engineer by trade, live in California so I know that will be a challenge.

It aims to redistribute US trade revenues to American citizens, excluding high-income earners, and is framed as a "reward for hardworking Americans" who support domestic production.