A "do it up" man is someone a single lady keeps on the side just in case her other two or three "side pieces" are busy. This guy is necessary in many ways. After a night out at the bar when you have been drinking with the girls a "do it up" man comes in handy. You have already spoken to "side pieces" 1 & 2, and they are way too intoxicated to show you a good time. So you call your "do it up" man to handle your business. It is essential that "do it up" man has his own place. He cannot live at home or have roomates, because when you are drunk enough for "do it up" man you are going to be acting a fool!!!
Hey girlie what you doing after this, going to the diner?? Hell no I'm calling "do it up" man. Girl you must be drunk to do that up. And hence, "do it up" man was born in a dive bar in the valley.