Most toyhaulers will have very large freshwater tanks, even the smaller ones can carry 100+ gallons. Just peruse the specs at various manufacturer websites, they all pretty much produce toy hauler rigs since they are so popular these days. Grand Design does make some very sharp looking toyhauler units, heard they have great customer service.
We prefer boondocking and with our 3 daughters, my wife, my son and I, we had no problem going several days without using the 110 gallons available on our less than 35' toyhauler. Finding a grey water tank that exactly matches huge FW tanks will be nearly impossible. Good luck, hope you find a rig that suits your needs and proves to be all you expected and more.
