What effects would not likely result from enacting a free trade agreement?

At their core, free trade agreements are promises made between nations about how they will deal with imports and exports. The most common issue involved in any free trade agreement is tariffs, special taxes imposed upon imports or exports.

In the absence of an agreement, nations have an incentive to impose tariffs. More precisely, interest groups in each nation have this incentive. Auto workers in the US might want there to be a tariff on Japanese automobiles, for example; this would drive up the price of Japanese cars and thus give US auto companies an advantage in US markets. Even if the nation as a whole would not benefit, it is often the case that particular groups with significant political power benefit from tariffs and can lobby the government to impose them.

But once another country imposes tariffs on your exports, you have reason to impose tariffs on theirs. When this happens, both countries suffer, because the unfair advantages for certain industries in certain countries undermines competition and makes the market less efficient. The US car manufacturers may sell more cars in the US,  but they sell fewer in Japan; and typically they actually lose more from the tariffs of other countries than they gain from the tariffs in their own.

A free trade agreement is meant to solve this problem, by getting both nations to agree to remove their tariffs simultaneously. This makes the market more competitive, and can have all of the following effects:

1. Prices of goods go down
2. Quantities sold of goods go up
3. Local industries lose business to foreign industries
4. Local industries gain business from foreign industries
(yes, both of these are possible simultaneously; often they happen in different industries---for example, the corn industry might benefit while the textile industry suffers.)
5. Overall economic welfare improves in both countries
6. Government tax revenue decreases (tariffs provide revenue)

Many real-world free trade agreements also include additional provisions that are not about tariffs; for example they might include price floors or price ceilings on certain products, or demand certain environmental policies, labor standards, or intellectual property protections. These are often the things that end up being debated when any new trade agreement is proposed, because they are much more complex and controversial than tariffs per se. Environmental regulations can be good, for example, if they really do protect the environment from needless destruction; but they can also be bad, if they are so strict that they make it impossible to do business. Certain kinds of labor protections are necessary to keep workers from being exploited by multinational corporations; but other labor regulations only add red tape and do little to protect workers. Intellectual property is meant to protect creators and incentivize innovation, but it can also create barriers to innovation and raise prices. As a result of these complexities, there is often considerable disagreement as to whether any particular provision of a trade agreement will actually do more good than harm.