That would be a horrendous server. You have 6 customers fighting over the IO of the single hard drive, then 256k VPS you're at 20 dollars and 3 customers to cover the 60 dollar cost of renting the server, then the next 3 for profit.
Minimum and best option is to buy a 5,000 dollar super micro with 5645 6x core HT cpu's at 2.4GHZ, 4 2TB Enterprise drives done in Raid 10, ideally with a SSD cached Raid card from adaptec I think that's who made one. Redundant power.
I like vps.net's offering because they are on app clouds, something I would like to offer someday but at minimum you're looking at a 20k investment in hardware alone plus at least 1000 a month for colocation and bandwidth.