There is really no such thing as an “international patent.” But based on certain treaties, when an inventor files a patent application in one country, he/she can file a patent application (usually within a year) in another country.
If you want international protection for your patent, you can (1) file in individual foreign countries, (2) file in jurisdictions that cover multiple countries (such as the European Patent Office (EPO)), or (3) you can file under the Patent Cooperation Treaty (PCT).
Filing in individual countries involves two steps. First, file an application with the USPTO. Second, within 12 months of your U.S. filing, file individual applications in countries where you want protection.
You should budget at least $20,000 per country for foreign patent protection. If the native language of the country is not English, then you should budget more (since translations will be required).
If you are making money from foreign customers, or if you expect your company to be acquired by a foreign company, then foreign patents probably make sense.