Now, maybe you are wondering are if you can have a wedding abroad. The answer to this question is yes; you can have a wedding ceremony and initially live abroad, and as long as your marriage was registered with local authorities, it will be recognized in the U.S. All you need as proof is your marriage certificate that recognized authorities have issued.
Still, there are some exceptions when USCIS will not recognize your marriage even if it is valid as such in the place you had the wedding ceremonies. This applies to polygamous relationships, underage marriages, domestic partnerships, proxy marriages where one person was not present during the ceremony, etc. Of course, the ones used often- relationships entered into for purely immigration purposes will not be accepted no matter where the wedding took place.
U.S. Citizenship and Immigration Services (USCIS) takes intentions to immigrate to the United States on the grounds of marriage fraud very seriously. If USCIS officers suspect you are not legally married, they may ask you to prove that your marriage is bona fides and formed from a genuine relationship.
This can be one of your tasks during the interview, or it could be enough to attach some evidence with your application (photos from your wedding, travel itineraries, joint bank accounts, etc). In addition, marrying a foreigner for money is illegal as well.
Immigration fraud can lead to a prison sentence, of up to five years, a fine of up to $250,000, or even both, according to the U.S. Code § 1325: Improper Entry by Alien.