What Bob said: Look in the neighborhood of the tank and you'll probably see a blue PEX pipe. Go back inside the MH and somewhere behind a drawer or removable panel in the vicinity of the blue PEX pipe you will probably find a 90 degree drain valve.
The drain on our Vegas is right off the tank under the couch. I tried it once and it was so slow I just used the water pump and emptied it into the gray tank through the faucets. I can pee faster than that drain works.