The cost of even a simple fence can be expensive if you have a lot of area to fence in. Landowners with horses or other animals who need to fence in many acres spend a huge amount on fence building and maintenance. Cheaper methods of creating fences are available, if you're willing to use your imagination and perhaps put a bit more work into it.
If you're lucky, you might find people who are removing a fence from their property and will give it to you if you're willing to cart it away. A fence acquired in this manner might not be in great shape, but if you're moving it anyway, you can dispose of any parts that are damaged or rotten and just use the good parts. Watch online trading sites such as Kijiji and Craigslist, or put your own message online, or a wanted sign in your community asking for fences that people might want removed.
An electric fence involves far fewer materials for its construction than a heavy wooden fence and, therefore, is cheaper and easier to install, although you then have to pay for the electricity to run it. Electric fences require only wire, posts and some electrical equipment. If you're looking at a large area that needs fencing, and you don't have much upfront capital to pay for it, an electric fence might be the best solution for you.
Hedges and Plants
In some areas of the world, fences have been created out of living plants for centuries. This method won't fill your fencing needs immediately, because it requires a number of years for the plants to grow large enough to be effective. Thorny and dense plants that are local to your area and are hardy are best, as they will thrive in your climate and can probably be bought more cheaply than plants that are imported from somewhere else. If you own a large parcel, find stands of young plants that can be used for fences. You might be able to carefully dig them up and replant them in lines where you want the fences to be. This method requires some long-term planning, but can result in a long-lasting, no-maintenance barrier that blends well into the landscape.
An effective, though not beautiful, fence can be made from shipping pallets. Line them up in a zigzag pattern and nail, screw, or lash their sides together to create a strong barrier. Millions of pallets are used every year, and many companies are happy to give them away. If you are searching for the cheapest fence, and aren't intimidated by a some hard work moving hundreds of pallets, this might be your best option.