An actual play example from one of my old RM games: all the PCs were wizards, and most had been built with decent meditation skills to facilitate the quick recovery of spell points. (RM is a spell points system, where points are recovered via rest and meditation can enhance rest). But one PC had been built by the player so as to sacrifice meditation skill for social and perception skills. Which meant he was having trouble recovering his spell points quickly enough to keep up. So the player had his PC go out into the shady part of town and purchase a spell-recovery drug. Which worked, but to which the PC (via the game's disease mechanics) became addicted. (Another comment: the player knew of the chance of addiction - it was not secret backstory. This is part of the idea of "overt", upfront stakes that is characteristic of indie play.)
Because the drug was expensive - something the player knew when his PC started using it - the PC quickly spent all his money on it. Which meant that he missed the annual rental payment on his house. And so ended up homeless.
Around the same time, he had another series of misadventures out in the field - in particular, being pushed off a floating disc by a demon that another PC had bound, but then lost control of in an dispel magic zone. On that particular occasion the PC was rescued by an NPC elven wizard, the agent of a rival power, who found him, invisible in the bushes at the base of the castle warded by the anti-magic. (This is an example of "fail forward". The PC has failed in his endeavour to navigate into the warded castle on a floating disc, but that results in a new complication rather than a narrative dead end.)
Despite initial suspicions, the two wizards - PC and NPC - became friends (the PC wizard, as I mentioned, was strong in social skills), then romantic partners, and this inspired the PC (as played by his player) to kick his addiction. Then the elven wizard NPC - who had abandoned her ties to the rival power in order to be with the PC wizard - got cut in two by another out-of-control demon summoned by the same other PC; and the PC (as played by his player) relapsed back into addiction.
The demon-summoning PC got sick of his companion's ineffectiveness due to the consequences of addiction, and so (i) paid an NPC cleric to cast the appropriate healing spells, and (ii) did a deal with the unhappy PC: if the unhappy PC would help the summoner PC and his allies conquer the hometown of the two, then as a tradeoff the unhappy PC would get his house back, and also a magistracy in the city (something he had long sought). The deal was agreed to, they helped in the conquest (which was adjudicated by "saying yes"), and the invaders kept their side of the bargain. So the unhappy got his house back and got his magistracy. All he had to do was betray his city at the behest of someone whose demons had nearly killed him, and had cut his only true friend in half.