Page 4 of paperback "The Decision" (Book 18). Ax talks of working for money so that he can buy cinnamon buns. He finds it necessary to explain the concept of "money" to his hypothetical Andalite readers, saying that money is an abstract human concept and that one gives amounts of money to various people in society in return for useful items. Ax's need to explain money implies that Adalites don't use money in their economy.
P 69 of "The Beginning" (A very misleading title, since this is the very last Animorphs book!). Marco talks of wealthy or influential Andalites coming to Earth, morphing human, and going off to the food courts to raid the Cinnabon and Mrs Fields. If Andalites don't have money, how can one tell that a particular Andalite is "wealthy"? (How do Andalites measure "wealth"?).
