I got offered aswell but I refused cause I already did it 7 years ago however it's to a non wl/ml. It was cheap too which I regret..
Long story short took 5 years to get PR, she took care of everything in terms of going through the paper work and immigration agent.
All I did was just pose In photos etc
It can be a hassle cause you may get calls to verify your legitimacy or even get agents rocking up to your house but for this to happen they need to be very suspicious.
Overall would I do it again? Maybe if the price is right
Also i got her to sign a prenup before we got married.