A network-based payment service provides various features for facilitating online, user-to-user payments. One feature involves the ability for users to define customized pay pages for receiving payments from other users. The pay pages are preferably hosted by a service provider site that handles the collection process, and may be created using pay page templates that specify the layouts and behaviors of the pay pages. In one embodiment, a pay page owner can also define one or more "pay boxes" to allow payments to be initiated from other web sites, which may include the web sites of associates who receive commissions on resulting payments. Another feature involves the ability for users to make single-action payments from web sites external to the service provider site. Also disclosed are various features for controlling access to content and services based on whether, or an extent to which, a visitor has made voluntary or mandatory payments.