I have exactly what you are looking for:
CashInterest.com
Not only is it virtually the ultimate domain for a site geared to those who have an "interest in cash," but as you can see it has the added and unique benefit of this double meaning for consumers and surfers also looking for "cash interest." At this time, I would let a buyer have it for an offer of $1,000 plus transaction expenses (PayPal, Escrow.com), but that might not last very long.
For an offer of $700 plus expenses, I would currently sell the shorter and brandable name CashLiquid.com