While it may be free, there is no one monitoring the barter ads, so you must be aware of potential Craigslist scams, and realize that you are always at risk when it comes to meetups and exchanges. For example, about a year ago, I arranged to trade massage gift certificates for housecleaning. Since the individual was coming to my home, I was more nervous than usual. However, she offered good previous references, and we  arranged for a time to meet when my husband would be home, in case an odd, unexpected, or even dangerous situation arose.
Adam Smith, the father of modern economics, sought to demonstrate that markets (and economies) pre-existed the state, and hence should be free of government regulation. He argued (against conventional wisdom) that money was not the creation of governments. Markets emerged, in his view, out of the division of labour, by which individuals began to specialize in specific crafts and hence had to depend on others for subsistence goods. These goods were first exchanged by barter. Specialization depended on trade, but was hindered by the "double coincidence of wants" which barter requires, i.e., for the exchange to occur, each participant must want what the other has. To complete this hypothetical history, craftsmen would stockpile one particular good, be it salt or metal, that they thought no one would refuse. This is the origin of money according to Smith. Money, as a universally desired medium of exchange, allows each half of the transaction to be separated.[2]
Michael Linton originated the term "local exchange trading system" (LETS) in 1983 and for a time ran the Comox Valley LETSystems in Courtenay, British Columbia.[22] LETS networks use interest-free local credit so direct swaps do not need to be made. For instance, a member may earn credit by doing childcare for one person and spend it later on carpentry with another person in the same network. In LETS, unlike other local currencies, no scrip is issued, but rather transactions are recorded in a central location open to all members. As credit is issued by the network members, for the benefit of the members themselves, LETS are considered mutual credit systems.
The history of bartering dates all the way back to 6000 BC. Introduced by Mesopotamia tribes, bartering was adopted by Phoenicians. Phoenicians bartered goods to those located in various other cities across oceans. Babylonian's also developed an improved bartering system. Goods were exchanged for food, tea, weapons, and spices. At times, human skulls were used as well. Salt was another popular item exchanged. Salt was so valuable that Roman soldiers' salaries were paid with it. In the Middle Ages, Europeans traveled around the globe to barter crafts and furs in exchange for silks and perfumes. Colonial Americans exchanged musket balls, deer skins, and wheat. When money was invented, bartering did not end, it become more organized.
In the United States, Karl Hess used bartering to make it harder for the IRS to seize his wages and as a form of tax resistance. Hess explained how he turned to barter in an op-ed for The New York Times in 1975.[24] However the IRS now requires barter exchanges to be reported as per the Tax Equity and Fiscal Responsibility Act of 1982. Barter exchanges are considered taxable revenue by the IRS and must be reported on a 1099-B form. According to the IRS, "The fair market value of goods and services exchanged must be included in the income of both parties."[25]
PERKS - Trade & Barter allows you to adjust the value of the Investor and Master Trader perks. This should work even if you have another mod that alters the Speech tree. Options: set either perk to 5000 max. You can set independently adjust the amounts required to invest and the amount of gold the merchant receives. However, when you make the initial investment, this money will be available until spent. Trade & Barter also adds to the Investor Perk by providing merchants with increased inventories when you invest in them. Increased inventories are unique to each individual merchant.

Fluctuating Gold - This option will add an additional random amount of gold to merchant inventories so that merchants don't always have a static amount of gold. This will be added to their base gold, so they will always have at least the base amount available. The random amounts have been set with regard to the vanilla gold amount and won't increase merchant gold drastically above the vanilla amounts.

As Orlove noted, barter may occur in commercial economies, usually during periods of monetary crisis. During such a crisis, currency may be in short supply, or highly devalued through hyperinflation. In such cases, money ceases to be the universal medium of exchange or standard of value. Money may be in such short supply that it becomes an item of barter itself rather than the means of exchange. Barter may also occur when people cannot afford to keep money (as when hyperinflation quickly devalues it).[15]