Doesnt really matter how much at first. Its the feeling that someone thinks your work is good enough to pay ANYTHING for, and will hang it up somewhere.
Selling your first print is the coolest feeling in the world. I've sold quite a few to my friends, my friends friends, and I even got one on the front page of a magazine (Tuna got one of his photos on the second issue of the mag, I believe)! Hope you sell more!