The difference is when you draw by memory you won't remember every tiny detail, and you make/draw it in your own way vs. having the object in front of you you can copy it almost exactly.
Not sure per month, but in a year they make around $127,800. So you could divide that by 12. Which would be 10,650 per month.
Vocal warm ups, breaks, tea with honey, practice in small portions, tone control
Beyoncé’s Lemonade is 10000000000000000000000x better