“I visited the U.S. last Christmas, and I was offered a job in the restaurant industry in New York, which I am going to soon take. I used the visa waiver program for my last trip and it worked great, and I’m planning on doing the same this time around because the job starts soon and I need to be there. How will this work if my employer wants to sponsor me for a visa, which he has said he will do?”
Those who enter the U.S. using the visa waiver program have no options as regards to changing their status while remaining in the country. In other words, if the opportunity of a visa arose for you, processing would have to take place in the country where you normally reside.  
If you overstay the visa waiver and eventually return home if a future visa becomes available, you run the serious risk of being barred from the U.S. upon return – a three-year bar would kick in for overstays of six months to a year; this jumps to a 10-year ban for those remaining here for more than a year.
Therefore, you’ll have to decide how you want to live your life here. If you remain past the 90-day authorized stay and become undocumented, the immigration legislation now under debate would not offer you any relief, at least not in its present form.