It's an investment for a bank which is middle way between regular loan/bond (where you get fixed interest and 100% of the loan at the end, but no appreciation)

It's an investment for a bank which is middle way between regular loan/bond (where you get fixed interest and 100% of the loan at the end, but no appreciation) and stock share (where you get no fixed interest and all the appreciation when you sell it). The hybrid product would be you get some interest and some of the appreciation, but not as much interest as for a loan, and not all the appreciation at the end. How much would obviously be negotiated depending on interest rates, projected appreciation, and other factors. The point here would be to defer paying the interest (to make the asset owner's life easier while they are alive) while leave enough enticement for the bank to agree to the whole scheme (banks usually don't just buy shares in people's 401k's). I do not know which combination specifically works but it doesn't seem implausible for me for such combination to exist.