Took a look, and it does appear that paypal is now offering a password management service (
https://www.paypal.com/us/cgi-bin/webscr?cmd=p/xcl/rec/subscription-pass-manual-outside) for subscriptions and recurring payments, however it appears to be fairly complicated for installation, and as this would be in fact giving your users usernames/passwords to paypal.
This would be a security risk for anyone who is using your site, as if paypal stores the usernames and passwords (you have to assume they do) and paypal were ever compromised then all of your users usernames and password could be at risk.
Implementation of the usernames and password would depend on the type of script you are using, and if your script contains its own username/password database, you may need to manually add the usernames and passwords to the database/script from the file that paypal sends to the file on your account.