The short answer is nobody knows.
Once Congress appropriates this money and the President signs the bill into law all we will know is that around 800 billion dollars will be authorized for spending for the purpose of economic stimulus. The US Treasury will then go about getting the money for Congress to spend...except it's not there.
The Treasury will go to the Federal Reserve and they will go about doing all that they can to procure the money. We have no idea what the Federal Reserve will need to do in order to get this much money. After all of the bailouts it's not likely they will be able to borrow all of it without dramatically raising interest rates. How will this impact the economy? The very act of getting the money to stimulate the economy may end up dragging it down further. The average congressman has NO IDEA what will be required to get the dollar figure they are appropriating.
- If it is borrowed interest rates will be forced to rise
- If it is monetized then inflation will rise
- If it is taxed then the private economy shrinks
It would be nice to hear just once, someone in government (besides Ron Paul) acknowledge that the simple act of securing this money could do great damage alone before it is even spent.