The USCIS may grant permission for your fiance to take up employment in the U.S. before the marriage takes place. To obtain Employment Authorization your fiance will need to file Form I-765, Application for Employment Authorization, with the USCIS Service Center which covers your fiance's place of residence in the U.S after your fiance's arrival there.M
Note: The USCIS is currently taking 90-120 days to process EAD applications and the authorized stay for a K-1 fiancee is only 90 days, therefore you may not receive the EAD in a timely manner, The EAD can only be valid for the period of authorized stay.
The fiance visa petition cannot be filed until you are both legally free to marry. Therefore, you will be required to wait until your fiance's divorce is finalized.
If you are traveling to the U.S. to marry a U.S. citizen with the intention of returning to your place of permanent residence abroad, you may apply for a visitor (B-2) visa, or if eligible, travel without a visa under the Visa Waiver Program. Evidence of a residence abroad to which the B-2 visa holder or visa wavier traveler intends returning should be carried for presentation to an immigrant inspector at the port of entry.