Are there any mechanics you're thinking about? How close to the game are you planning on creating this RP? Is it going to be canon or original? Is it going to be a "standard" Pokemon journey from the beginning or are they going to be trainers of various levels of achievement? 

There are quite a few Pokemon RPs throughout this forum. Furthermore, just posting in an Interest Check that you're thinking about creating a Pokemon RP would be a good start. It won't be too helpful to post here for a Co-GM when you don't seem to have a story, setting, or plot.