Monday, Wednesday, and Friday, Harry walks a total of 3 * 7 = <<3*7=21>>21 dogs.
Thus, in a week he walks 21 + 12 + 9 = <<21+12+9=42>>42 dogs.
At a rate of $5 per dog, Harry ears $5 * 42 = $<<5*42=210>>210 per week.
#### 210