106:7 It is permitted to lend money with interest to a non-Jew who is a regular customer because it’s considered a loss if his client becomes accustomed to going to someone else. If he lent money to a non-Jew who isn’t a regular customer, he should spend the interest earned during chol hamoed on things for the joy of yom tov. One may not, on chol hamoed, sell merchandise to a non-Jew who isn’t a regular customer of his, despite whatever he might add towards the joy of yom tov. One may sell to a regular customer since it would be a loss if his customer started going to someone else.
106:8 Changing money is not allowed on chol hamoed.