If you want to put a Verizon phone on PayGo, your best bet is Page Plus. They are one of the few companies that let you bring your own phone and they use the Verizon network. I have a Droid 1 phone on them now. The plan I use is called "The 12" which for a whole $12 a month gives me 250 minutes, 250 SMS and 10MB of data. Using Wifi at home and work (same place) means I really don't need don't need much data when I am elsewhere.
Here is a grid that shows prices of most of the companies so you can compare prices:
Prepaid Compare