There are no limits. The only limit is what a specific brokerage requires. For instance if you need $2,000 to open up an account with a specific broker then that is all that is required.
Some brokers might have limits on when you can start trading options. For instance they may require you to have made so many trades in the past before they allow you to trade options. But other brokers like thinkorswim will allow you to trade options as long as you open up an account.
I would think futures markets work the same way, you just need to find a broker that allows you to trades futures.
