Go to the Greek Quad and stand near the frat boy who buys pictures. With your back facing the frat boy, take out your camera and snap pictures of the cheerleaders that are practicing. After taking all the pictures, turn around and sell them to the frat boy. He will charge $6 and will give you $4 for each picture. If you stand too close to the cheerleaders they will react to the flash and you will get less money for the pictures. This can be done repeatedly without penalty.
This trick requires the "Naughty" item and having both Analisa and Luba at the dance club. Enable "Naughty mode" and go to the dance club. Take pictures that frame both Analisa and Luba while they are posing. Each picture if taken properly gives you more than $20. That is more than $120 per set. There are other combinations that will give you large sums of money; just remember to take pictures of as many women as possible in a single frame.
Go to Lefty Too's and play the wet t shirt game. It is easy to win, and you get $10 when you do so.