Notwithstanding the sign on bonus you will make 64 hours per month plus per diem during training. I believe they are starting new FOs at pay step 3, so $38.28/hr. 64 hours * $38.28 = $2,449.92, plus 24 hours * 30 days * $1.90 per diem of $1,368.00, so during training for a full month you’ll see $3,817.92 pre-tax. Once you’re on the line it will be 75 hours ($2,871) for reserve or the line value (upwards of 91 hours if you get a strong line) plus perdiem (depending on flying).
As upgrades now are instant for those who have part 121 time required for FAR 121.436, if you have no 121 time I would expect it to be a bit longer. Probably 2-2.5 years, as it will take 1.5-2 years to get your flight time and you’re being hired after a glut of first officers all scrambling for time to upgrade.