First of all, you may wish to read from the how-to topics at enotes about how to write a persuasive essay (listed as an argumentative essay).  On this page is a list of the things to do, one of which is to do some research on the subject and obtain testimony from authorities. 

In preparation for your argument, write down the pros and cons on a worksheet.  Then, you need to prepare your facts, etc. that can counter the cons. 

On the pro side, there are sound reasons why community involvement is important.  The acts of unselfishness that people perform are certainly beneficial to the individual person's sense of fulfillment; afterall, as Joseph Conrad wrote in "The Secret Sharer," meaning depends upon sharing.  Giving is a rewarding experience, for it aids both the giver and the ones who receive.

Check out the site listed; it will assist you well.  Good Luck!