typically how it works is this. a micro e mini contract has a 17k size, varies depending on price of S&p 500 times 5. thats the size of his exposure. when you buy that contract, you dont have to put the entire 17k down. depending on the margin requirement for brokerage it can vary between 3% to 30% down payment. the lower the down payment, the fast you will blow up and get a margin call. so you can essentially have a leverage of 3x to 30x.
the e mini used to be the standard, but because S&P 500 rose so much, they created the micro so poorer people can speculate, but its essentially same thing. if you did e mini your exposure would be 170k. its about 10x the size.
ive never traded it. but the places if you wanted to trade it via a regular brokerage, td ameritrade and interactive allows you to.