Why would you want to do this? Save money, gas? Don't want a "big" vehicle?
A small vehicle and engine worked at or above it's design limits will generally lead a shorter life. Fuel consumed will be similar if not more than a larger engine not working as hard.
Counting every pound when you pack to go on a trip is not fun. Neither is telling your friends or family they can't come along because you don't have the capacity. Are you aware that a vehicle's tow rating decreases as you add weight to the vehicle. If a 4 cyl. RAV is rated to pull 1,500 pounds that's likely an empty one. If you put 500 pounds of people, pets, and gear in the RAV your tow capacity is likely only 1,000. However, the new SAE ratings may be changing how tow ratings are computed.
In my opinion towing with something like that will leave you going slow up the hills, worried about packing, not saving any gas, and wearing the parts out fast.