You also need to let us know your desired price and probably the screen sot of the cpanel home page for proof of availability of the product.
Also try to answer this question - this shall allow shared webhosting and space used by one account affects the other?
http://imgur.com/a/5yctN
As for your question technically yes. If you have one guy using an absurd amount of disk space like 500 GB then it may affect the others but you can set limits. You most likely won't have any problems like that and just to make sure you don't just be sure to set limits on the disk space each customer can use.