I bought my first bike from Wal Mart when I wanted to learn how to ride a bike (I was 17 years old). It was a Roadmaster mountain bike that cost only $55 including tax. I crashed it into a fence a few times while learning how to ride. It took me only 2 days to learn how to ride a bike. I rode it to school for a few months.
The brake cables got loose and then the rear brake cable snapped. The front brake still worked. Then the bike started to have shifting problems. The bike had been ridden less than 200 miles, but it half-paid for itself in gas savings, back when gas was $2. I then went to the LBS and bought a hybrid bike for $350, and a u-lock for $40, and that still works to this day with over 3000 miles on it. I left the Wal Mart bike unlocked outside, it took a week for it to disappear, and then after it was stolen, it came back to a different bike rack a day later, and the next day it was stolen or thrown out for good. Wal Mart bikes suck so much, thieves don't even want to steal them.