Howdy Goon,
George Semel makes it sound like it is....Hard. The good old days are over. It really is a career nowadays and not a way to build hours as it used to be. I spent 5 years in the industry. It is hard work, a small industry and you gotta impress first time. Most spray pilots are country boys and they get the good seats by having good mechanical aptitude. You will be doing all types of different work, non-flying e.g. Changing the clutch on a truck, building the boss a new fence, anything. I have done alot of wierd stuff. Once you get experienced and established, you will work the seasons and do well.
If you really want to do it, go for it, but be wary of those Ag flight schools on the net, they are full of !!!!!. You only walk straight into a job if times are booming and there is a shortage, there is no shortage at the moment and times are not booming. But if you have great connections or.....you have loaded for some time and your employer has sent you off to get trained then you got it made.
All of this is just from what I have seen and experienced. I wish I was still doing it sometimes, it is great flying and not the "yeeha" bull!!!!!" that people make it out to be. Cowboys don't last long.
As far as green cards go, let me tell you, don't believe flight schools. Ask a lawyer.
Good luck.
DW