For the occasionally towed car, as opposed to a regularly used 2nd car, the older model Smart cars work great for about 1/3 the price of new. Also they're towable as they have an computer controlled clutch, rather than, torque converter. I understand the new Smart automatics aren't towable because they've done away with the much maligned computer operated clutch. Having owned and driven an early VW with 40 HP, the 70 HP Smart, weighing about the same, has more than adequate power and can be very entertaining, though a bit quirky, to drive. Shopping Craigslist for "by owner" Smart cars will yield many with very low mileage (20k-40k) in the $5,000 to $7,000 range. This includes the cabriolet versions;
Anyone interested in these cars who is concerned about their safety should visit their local Smart dealer and examine the "cutaway" display of their high strength steel cabin. There are also several YouTube crash videos showing how well the Smart design survives crash tests.
If the color of your toad is important, all the Smart car body panels are plastic and can be easily replaced or repainted to suit. We were fortunate to find one that matches the Solera color scheme.
Finally, you won't need a supplemental braking system. Even loaded, our Solera with Smart in tow weighs about 2,000 lbs UNDER the gross vehicle weight rating of the Solera. We've found almost no significant change in driving characteristics or fuel economy when towing the Smart. What a great surprise!