It really depends on what you want to do with the tow car. (and if you have a 'tolerant' travel partner
)
I keep a few choices available: (Motorhome = VW Rialta 20 mpg / 15 towing... temporarily, till I do a diesel conversion and get it up to 35mpg)
1) VW diesel Rabbit (1800#) 50 mpg /w sport suspension for mountain driving (cost was $300, but have a few extra 50 mpg Rabbits I got for $35)
2) VW GTD (Euro spec Turbo Diesel GTI) good at higher elevation (~46 mpg ~$1200 to build euro spec car from US GTI)
3) Work in process...4x4 Suzuki Samurai / VW Turbo Diesel conversion (
Suzuki Samurai Turbo Diesel conversion kit for Suzuki Samurai) 35 mpg off-road economy w/ diesel torque.
I am also working up a multi-hitch to take along a couple motorcycles (dual sport)
If I was desiring 'gas' power, and liked to spend $$, I would have a 2004 VW R32 as Dinghy
My mom used a Jeep Grand Cherokee for many yrs as a dinghy.
For a 'generic' I would use a Manual tranny Saturn. ~ 40 mpg
My next motorhome will probably be a Peterbuilt or Kenworth tractor and pull a set of drop deck doubles (One with living space and one with machine shop and dinghy 'on-board'). A nice queen sleeper on the tractor is really comfy way to make miles, but the trailer will be a must once I 'arrive'. Then I can take the tractor out and haul freight to earn more camping $$.