You can take courier jobs, for example. These jobs often have time limits, but the rewards for them are generally worth it. They can range from simple FedEx missions to missions that are more mercenary in nature. You're free to pick the jobs you want to do with them. However, if you fail to do courier jobs in the amount of time required often enough, you may find that courier stations are reluctant to hire you for these assignments.

Likewise, you can also make a living being a trader. Several towns offer positions where you buy something cheap and can sell it elsewhere for profit. They'll tell you about the goods they offer, and then tell you were you can sell them because the demand is high.

Unfortunately, though, you can't keep doing these routes and courier jobs in the same cities, because of the monsters eventually destroying those cities. At some point, you'll have to move on because no one stopped the threat to that region. Of course, that's not to say you can't decide to courier one region until it dies, and then move on and save the next. It's up to you.
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