Both IRA and 401(k) plans are subject to this tax.Tax on UDFI (unrelated debt-financed income) is generated when a tax exempt entity uses debt-financing as part of funding an investment. 

Many investors in your situation also explore seller financing or subject-to deals to minimize upfront costs, especially if they find a seller open to creative terms. 

The second DOS was in 2020 when I bought enough properties using "subject to" that I couldn't keep up with rehabbing and some sat for a couple of months.

That said, I will still try to provide some “clarity”.Purchasing a property “subject to “ the existing debt can be done two ways.  

Some will let you rent your primary and still do a DSCR loan on the subject, however, this would come with the added scrutiny of really documenting and evidencing you have no intention of moving in to the subject.  

The more you can make your screening objective than subjective the easier and more successful everything will be.

I have some basic knowledge about the subject.

All real estate activities you engage in ad a licensee are subject to your broker supervision, and fall under the regulatory rules of your state's real estate commission or department of licensure.

However, I've NEVER had a note called on any properties and the vast majority were "subject too" and/or owner financing.

These included cash buys for flips, seller financing, and subject-to deals.