Anything from a minute to three months. Depends on what your friend wants to teach you.
Cost:
Nothing, unless your friend is a cheap ass.
Cons:
You might feel stupid and clumpsy when you can't walk on your hands while your friend does it with such ease. The Tom & Jerry-toy might break if you drop it on the ground.
Pros:
You get nice arm muscles from walking on your hands. You and your friend become closer.
THIS IS NOT ANOTHER GLOSSY FASHION BLOG. THIS ISN'T A MOBILE PHONE YOU CAN BUY. IT DOESN'T CONTAIN CYNICISM OR IRONY. IT'S ONE THING YOU CAN DO EACH DAY ALL OF 2010. 365 THINGS YOU CAN DO - THE BLOG THAT CHANGES YOUR LIFE.