Futures Questions

Hello. I have traded Forex off and on with real/fake money for over a year now. I've recently stumbled upon new insights and information that have helped my trading experience and knowledge immensely. I don't plan on trading futures until I've acquired enough capital, through forex, to do so.
How much capital would I need to trade the e-mini and the euro fx? How does margin work in Futures? Is it like FX where with an opening of a trade, some capital is taken out of your account?
Is there any demo account websites I can open to continuing my practice? I've used most of my 30 day trial with the broker Infinity AT.
I believe my approach in FX will be successful futures and I stand by that, as long as I execute effectively. Learning with real money is the key to learning I think.