The way its done is to push through favorable laws for a company with a wink and a nod, and then come back and work for the company as a consultant/lobbyist with a minimum 1 million dollar per year salary.
Billy Tauzin did this quite well with PhRMA (lobbying group for pharma companies). He headed up the committee which oversees drug companies and led the push to pass the Medicare Prescription Drug Bill which was quite favorable to drug companies. The bill among other things allows drug companies to set an arbitrary price for the drug without Medicare having the option to negotiate on prices.
As soon as the bill was passed he retired from Congress to lead PhRMA with a $2.5 million USD per year salary. Mission complete.