There's nothing preventing you from doing so, but I'd caution you about DreamHost's policies which hold you accountable for the actions of those you give access to your account's hosting. If they do something against the terms of service, you may find your entire account shut down.
But if you're willing to either take that chance, only resell to trusted parties, or monitor all the sites under your account, go for it! Let us know how it turns out.
BTW, I don't mean to sound discouraging, but I want to make sure you know what you're getting into. You should note that on the forums here we only hear from people who have had trouble. The ones who are happy mostly don't drop in out of the blue and talk about how their reselling is going.
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