Note: The feature is supported in X-Cart 5.4.x and earlier.
With the Memberships for Payment Methods add-on, you can give additional payment options to specific groups of customers in your store, e.g., enabling PayPal Express Checkout for wholesale buyers only.
After installing the add-on, a special Memberships field will appear under each payment method on the Payment Methods page of your store’s Admin area.
X-Cart 5.4.x - Store Setup > Payment Methods
You will need to use this field to specify the membership the payment method should be available. Then, your customers can see only the payment methods available to their membership group at checkout.