Just go for it man!
Get a used boat (cause you're gonna beat the crap out of it).....you know some runs if you've gone commercial or ridden with friends. Get on the oars....or find some friends that want to bum rides off you.
There will be plenty of peeps on this forum that will gladly have you along on trips and give some rowing/guiding pointers..........but finding someone to hop on with and take their oars/guide stick might be a little harder.
Get a boat, be diligent with safety, dig in.