Fiancé(e) visas are non-immigrant visas that are meant for the fiancé(e)s of US citizens. US citizens can bring their fiancé(e)s to the United States, by getting them fiancé(e) visas and get married to them in America. If you wish to bring your fiancé(e) to America, you need to file a petition for a K-1 fiancé(e) visa. Remember that only US citizens can file US visa applications for their fiancé(e)s and bring them to America.
K-1 fiancé(e) visas are good only for a 90 day period and you being a US citizen must get married to your fiancé(e) within 90 days. If not, your fiancé(e) must leave the country. While applying for a K-1 visa, you need to establish that you and your fiancé(e) have met each other in person. Moreover, you need to prove that you and your fiancé(e) intend to marry each other.
At the same time, you must be capable of financially supporting your fiancé(e) and you need to meet the income requirements. The most important thing that you need to remember is that you must get married to your fiancé(e) within 90 days. If you and your fiancé(e) fail to get married within the 90 day period, your fiancé(e) will be required to return to his/her home country.
To bring your fiancé(e) again to America, you will have to sponsor your fiancé(e) by filing an application for a K-1 fiancé(e) and you must go through the visa application process again. USCIS issues more than 27,000 K-1 visas every year. USCIS rejects very few applications and approves most of the US visa applications that the US citizens file on behalf of their fiancé(e)s.
K-1 visa holders will also be permitted to work in America. But they need to get employment authorization documents, to work legally in America. Your fiancé(e) can apply for a work permit soon after getting into the United States. However, USCIS will issue fiancé(e) visas only to the foreign nationals who are admissible into America and who prove that they have maintained clean records.