Overview: In simple terms trading in the futures market you are trading assets (commodities or financial markets) on margin, which if the contract was held until contract closure the trader would be responsible to take ownership or make a sale of the product.
In practice for myself and most other traders this does not happen as contracts are rarely held past the close of a trading session. To trade in futures you will need money to cover the margin required for a market you are trading and the commissions and fees needed to make the trade (entry and exit). Link to Ninja Trader Contract details given below:
Example: if you wanted to trade one contract of NQ (E-Mini Nasdaq 100) you would need $1000 in your account and $4-$7 to cover the transaction fees.
Links / Information: I am not a expert on futures, and I am in no way a financial advisor, the following are some good websites to learn more.
https://www.cmegroup.com/education.html
https://www.investopedia.com/terms/f/futures.asp
Honest Information 