Create a Single Use Password Protected area on my website

I need a single use password to be created to access a particular page. This password should be generated and emailed upon receiving payment. So: user will click some link/URL to access this "Protected Page" upon which time the user should be prompted to make a Paypal payment of (say) $4.99 Once the user makes the payment, the system should instantly detect payment received, and generate this single use password. The single use password should automatically be emailed to their email address. User is then taken back to access the protected page where he must enter the password that was mailed to the user's email address. Upon the user correctly entering the password he can actually access the "Protected Page" and the password is destroyed. So much so that if the same user tries to come back to the same page/url/link he will be required to pay again. This system will run on a dedicated server. It should ideally be built for PHP and WordPress. PLEASE NO BIDS OVER $100. PLEASE ASK ALL QUESTIONS BEFORE ACCEPTING THIS JOB.