There are loans marketed as interest only, but my understanding is that even with these loans the payment of the capital is deferred to the end of the term, not that you don't have to pay it back at all.
There are annuities, a financial instrument where the seller receives a lump sum and then pays back a fixed amount in perpetuity but I think only insurance companies sell these.
I think the most likely scheme is what the other comment is suggesting, refinancing the loan repeatedly
That's exactly how they work. As long as you keep making interest payments, and the value of the asset you took the loan against remains above a pre-defined threshold, you never need pay back the principal. The idea being that you invest the money you borrowed and earn a profit on the difference between the interest payment and your investment return. And the interest payment itself is tax-deductible because you borrowed to invest. Neat trick, right?
Btw, this is a power also available to ordinary people, in the form of a HELOC.
I mean, I'm glad I didn't HELOC my way to a few Bitcoin last month, so maybe it's best we leave these tricks to the rich folk anyway.