Lots of lawyer websites explain the process. Including this lawyers website.
https://immigration.com/greencard/e...cards/employment-based-eb-green-card-overview
EB2 or EB3 with PERM are most common. The employer must demonstrate they cannot find a qualified US Citizen to do the job (through PERM)
Employer must pay for PWD, PERM, I-140. (approx $10-20k USCIS fees & lawyer fees)
Employee can pay Premium Processing for I-140 (approx $1k) for two week decision vs 5-8 month decision.
Employers typically do pay, but not required, for AOS / I-485 for employee and dependents (spouse & children <21. Approx $3-5k
Most employers will require an employee contract to pay back related GC fees if you quit your job. (typically the fees paid in last year).
Most employers will not start EB2 or EB3 GC process until you have worked at least six months in the role.
TN to H1B to GC is preferred by some employers (takes longer, but allows for travel outside US during AOS).
TN directly to GC is possible, but requires almost one year stuck in US. Must wait 90 days from last entry before you and file AOS/I-485/EAD/AP, then current wait time for EAD/AP is 6-8 months. You cannot leave US for any reason (vacation, business trip, sick relative, etc) or your AOS will be considered abandoned, due to nature of TN status (non-immigration intent status).
Also if county of birth is India or China, their is wait time before you can apply for AOS. (India is really long wait time, currently 10+ years, forecast to be much longer for people starting GC process now).
I did TN to H1B to GC in under four years. I paid for I-140 premium processing ($1k) and spouse and dependent EAD/SSN ($200 legal fees), otherwise my employer paid for every thing else. Read these forums. But understand most people that post questions here are have difficulty, the ones that go smoothly are not posting on this forum.
