I help engines spin and pants stay up. What am I?

With no hammer or any kind of tool I build my house so quickly. What am I?

You can earn me, you can lose me, but you can't use me, either high or low, I can tell your status quo, either good or bad, it might make you happy or sad. What am I?

I am a important part of your body.

i have legs but no feet kids sometimes use me for something what am i