The lengtyh of sewer hose depends on RV park and where your vales are located. I have been in RV parks where the sewer connection is in the very rear & I have had to pull all the way forward for slide clearance. I have a 15' section I normally use all the time. Recently I had to run over to a local Walmart to buy more hose. I like several short lengths of hose. Only use what I need.
I tow 4 down. A trailer or tow dolly adds more weight. Not sure what they cost. Setting up for towing 4 down cost me about $2200.