If you manage a controlled circulation SimpleCirc can qualify your subscribers when they order their subscription and re-qualify them when it's time to renew. All of the questions you ask will be displayed at the top of the form and you determine which questions and answers will qualify the subscriber.
By default, your qualified subscribers will be offered a free subscription with a term equal to your qualification limit. If their answers to the qualifying questions disqualifies them they will then be presented with the option to purchase a subscription.
When subscribers renew their subscriptions they will again be re-qualified and their total term will be subject to your requalification limit ensuring that they never exceeed that limit.
All of your qualifying information is available for reporting on and can be included in BPA and AAM audit reports.
In conclusion, SimpleCirc makes it simple to manage your qualified circulation. Instead of trying to qualify your subscribers on your own site and then redirect them to a different checkout page, just link your "subscribe button" to SimpleCirc and let us take care of everything.