Legal

Farming
Farming is a good way to make money if you're just starting off because you don't need a license. Although, it is recommended you buy a license once you can afford it for extra income. Simply collect peaches or apples from an orchard from a field marked on the map. These can then be sold at a market for a profit. You should be sure to fill your car to by hitting "T" in the driver's seat. You can press "Y" to view how many you're currently carrying.

Fishing
Fishing is a relatively easy job to take on, but requires a bit more to prepare for compared to farming. To fish, you need to buy a boat and a boating license. Drive your boat into deep enough water, slow to a halt, and cast your net. Fish will be around the map in hot spots, so if your net comes up empty, try repositioning. Caught fish can then be sold to the Fish Market vendor.

Oil
Oil is one of the best, and easiest (legal) ways to earn money as a civilian. Below I will go over the basic proccesses needed to have intercourse with women and aqquire currency.

What you'll need Process Tips
 * Plenty of time, at least an hour and a half per run
 * A vehicle with a (fairly) large storage. Though you may not be able to afford one at first, after a few runs a HEMMT truck is worth the investment! (Eventually an Orca)
 * An oil processing license - this can be bought at the oil processor and is required to process and sell your oil
 * A pickaxe costs $1,200 at the General Store (required to mine oil)
 * An idea of what route you will take from Oil Field > Oil processor > Oil Trader. The fastest, and safest routes bring you the greatest profit
 * A backpack or vest so you can carry more oil on your person
 * Drive to the oil fields
 * Hit Y and open your inventory
 * Click on the pickaxe
 * Click USE
 * Once you see the message that you've picked up x amount of oil
 * Once your inventory is full look at your vehicle and hit T
 * Place all the oil from your person to the vehicle and continue - Repeat until both the vehicle's inventory and your own inventory is full
 * Drive to the processor and begin unloading the oil to process. (PROCESSED OIL TAKES UP LESS ROOM THAN UNPROCESSED)
 * Once all your oil is ready it's time to hit the road one last time, head to the oil trader and sell your oil
 * Yes you will run into bandits on the fields and other stops that want your hard earned money without doing any work, it's best to take in your surroundings before stopping, and always keep aware whilst mining. You may also want to acquire a weapon, along with a license, so you can defend yourself in this event.
 * Follow the laws: If cops see an HEMMTT truck they'll try to find any reason to pull you over (try to find drugs) thus wasting your time and causing a potential disaster. (We've all had stolen vehicles and have been killed by other players while arrested)
 * Take your time, yes oil takes time. There's no fast way to earn money, you're gonna have to work. The more shortcuts you take the greater the risks.

Happy money making.