Found some info after a light google search:
If pilot is offered a position by airline, pilot signs a contract with OMS requiring an upfront payment to OMS of $3,000 followed by 48 monthly payments of $800 (total $38,400) which commence when pilot begins working for the airline.
The legal/immigration process will take approximately 12-18 months to complete.
When pilot starts work, pilot starts making the monthly payments described above to OMS.
https://www.pprune.org/north-america/589993-foreign-pilot-agency-promising-visas.html