Do you have to pay for dc universe online

The game is free to play.
However, if you spend over £5, you get premium, which gives a few bonuses like money cap increase.
If you pay £8-9 monthly, you will receive legendary status and have unlimited cash limit, free monthly replay tokens (150 tokens), free monthly sevencash (500 sevencash), ALL of the current and future DLCs available (only while legendary - if you stop paying, you don't get DLCs), and some other minor bonuses.