The vermin are running rampant and the farmers are in need of assistance.
Step into Vermin Hunter and clear out the vermin that are wreaking havoc on the farms. The rats are eating the grain, the rabbits are destroying the vegetable patches and the pigs are eating everything else.

When you start, you are equipped with a basic pellet gun. This may not be the best weapon to use but it does get the job done...eventually.
But do not let this hold you back. You will earn currency for killing the vermin which you can later use to buy upgrades and bait (which helps attract the vermin to your desired killing spot) but be careful, do not kill any of the farmers live stock, because you will loose currency for killing the wrong animals.

Be patient in the beginning, while you hunt with just your air rifle, and make sure you save up as much currency as you can to get those much needed upgrades.