Help with a plugin (wordpress)

Hello!

I am looking for a plugin (pref free one since it's for my low investment project) that will show "join to the newsletter to read more" in blog posts. I would like to show the first paragraph or two and hide the rest below pay with email block.
I am not sure how it could work for users that will come back - if there is no plugin for that, I would also be interested in "tweet to read."

Do you know any good plugin which will not slow down the site?