Custom E-mail after Paypal Subscription Sign up

Hi, this project should be very simple for someone familiar. I have a few paypal subscription buttons. I use these buttons on my Wordpress website. I would like to be able to send custom e-mails to users when they purchase a specific subscription in addition to the paypal generated receipt. They do not need an account, or special membership features or anything tied in with Wordpress per-say. This is apparently non existent right now. A procedure, piece of software, plugin, even a set of instructions to set up a customized e-mail for a paypal subscribe button, that's all I'm looking for. I just want an easy method for creating a custom thank you/instruction e-mail for each subscription based button I create. Even if you are simply laying out a set of advanced variables or a script to modify that I can run on my Wordpress site, that is fine. I specifically do not want a bunch of bloat ware that is attached to my Wordpress install in the form of a large scale e-commerce solution. BONUS: Make it when people sign up for the subscription that their e-mail is sent to Mailchimp for bonus income, otherwise I would prefer to keep this project at $50.