@Kaarme
I'm not entirely sure he really needed Roxanne, but the trader (and the fact that she's hot and has fluffy ears) completely convinced him he did.
The MC would have been set for cash for a while from his initial bounties, then could have done solo runs in the labyrinth, picked up a couple of bounties on bandits, moved on to another town before other bandits started targeting him, and then done the same thing all over again. Rinse and repeat.
Honestly, it's the fact that the MC didn't need to make the purchase that actually sells this part of the story - it's not one more "you've got to save the world!", "I showed up in another world and saved/met a girl, so now I guess I'm doing this 'hero' thing?", or a "summoned to another world by jerks, betrayed by everybody I trusted - well, shit" plot. He got persuaded into something, bought the whole deal hook, line, and sinker (not really a bad deal, all things, particularly fluffy tails, considered), and decided that was his short-term goal. Then started working at it.
It feels like he made a real decision, instead of many stories of this kind which feel like "BUT THOU MUST!" JRPG plots, "I'm a monster and must endlessly levelgrind until nobody will dare fuck with me", "somehow bitches keep falling into my lap", or "hmm. Guess I'll just fuck around as a farmer or shopkeeper and lead the slow life" stories. Not that there's anything wrong with the types I've mentioned, but it feels like this dude has agency, instead of just kinda being at the mercy of the plot.