Current S/O to J/FO time to upgrade is around 3 years and 10 months. Then J/FO for about another 1 year. Once you qualify as F/O you can be transfered to a base dependant on fleet and the companies requirements. Of course one way of doing it would be to join as S/O and after a year or so (end of probation) transfer to freighters as F/O on the base of your choice.
AF