The Chochmas Adam writes that there was a custom in vilna to be meikel to lend with interest. Reuven wanted to borrow from shimon and pay interest. Even if Reuven had no assets he would approach shimon and be modeh that he has tangible movable assets that are worth 10k. Reuven agrees to sell these item to shimon for 8k that shimon will be paying for today. Shimon agrees to provide Reuven either with these items or with 8k plus 20% instead (which will still be less than the objects worht 10k that reuven would otherwise have to give to shimon). This type of set up is done so that reuven never becomes a borrower from shimon, rather he agrees to provide him with the merchandise that shimon purchased or with something to replace the merchandise, namely 8k + 20%. The main issue that the chochmas adam has with this heter is that the entire hoda'ah that reuven actually posseses these items is complete sheker and therefore cannot be used. However, in a case where reuven actually does have items that are worth 10k, he allows such a deal. The binas adam (5) tries to justify why the rabbonim are meikel to allow even the first type of deal through hoda'ah. He suggests that the ribbis in this case isn't d'oraysa, only d'rabonon and in a situation where people are pressed for parnassah there is room to be meikel with ribbis d'rabonon, but it is certainly not an ideal way to pay interest.