If you are unfamiliar with the Metro, get something like a Honda. Don't get me wrong, I love my Metro, but if you don't know what you are looking for, you may be stuck with a rusted out car running on 2 cylinders. Most Metro owners I know have a strange passion for these cars and fix them themselves since they are simple to work on.
If you really want a Metro, find a rust-free southern/western car regardless of running condition, remove the engine and trans and have the entire engine compartment and body repainted. Rebuild the engine with quality upgrades like the economy cam and gear offered through
3 Tech Performance and put it all back together. This will give you the power you need and make the 3 cylinder perform better. Then with proper love and maintenance, you will have a great ride.
I am currently saving up for a 3Tech economy grind cam and 8 degree cam gear for mine since I spent a few hours reading the reviews on those items.
Rust free car running or not would cost anywhere between $300 - $7000 depending on condition. If you find one for under a grand, then you got way more then enough money to fix it up like a new car.
Granted, my Metro has some rust issues, but if you read my Metro page (see sig) you will see that I have less than $1000 in my car including purchase price. I would not sell it for $5000 since it saves me that much in fuel per year.