Eh, it's a mindset thing @Dave DeMarinis
From a lending perspective 100% CLTV is obviously horrible, but this is more annuity than loan. Follow...
Custodian retirement accounts are hard enough to find suitable vehicles to generate good returns on (especially if you're not an accredited investor), and JV deals trigger UBIT, but straight interest won't. Loaning a flipper 100% money or gap financing can be treacherous, but show me someone who lives around and owns 10 SFR rentals in a small town and suddenly I'm piqued by their business model. If each house is worth $150,000 and rents for around $1,500 and they've got 70% NOO first loans at 5%, that's $565 in mortgage. My $45,000 costs $300 a month to be in second position and if taxes/ins/expenses are another $400 a month, they are cash flowing $200-300 a month, which obviously only grows as rents increase and my lien looks better and better as the principal decreases.
Now, sure, I'm painting a choice scenario...1% rent rule, an investor with that kind of SFR farm...but funny enough...I see more and more of those scenarios existing the more I talk to people. Point being, there are way more landlords like this who exist than I expected, just as there are a ton of private individuals with self-directed custodian accounts who consistently look for 8-10% returns that don't cause too much brain damage.
The structure may not be for everyone (nor do I put any of these types of deals together personally), but they exist. And if the real estate investor is competent, those retirement account holders are often happy with the results.