You can not use the same credit-card for two account applications, in such cases the second application will likely result in a 'credit-card already in system' error.
Also, it seems that the DreamHost TOS specifically forbids you from holding multiple hosting plans, below is a quote from the TOS.
[color=#0000CC]"The Customer agrees to hold only one (1) active web hosting service plan at any given time with DreamHost Webhosting. Signing up for multiple plans is grounds for termination of all additional plans without warning."[/color]
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