Like everyone is not the same, neither are bbws. We come in a variety of packages. Are you a plumper? BBw? SSbbw? Pearshaped? Hourglass? Top Heavy?
Knowing your niche helps you with marketing yourself. It will help you capture potential customers attention. After you figure out your body (pretty easy) is figuring out what is going to sell for you.
Are you a Milf? Gainer? Goddess? Femdom? etc. There are many more categories as you know. I suggest you research and ask your fans constantly for input on what to produce.
These are the video clips I sold from Jun 1st 2014 to June 29th 2014
Most are around 2 minutes long. There are a number of different fetishes. I focus mainly on gaining since that is where I make most of my money. I had to break it into two photos because of how long the page was.
On every clips4sale site there is a box for top selling clips. I would suggest taking a look at performers with similar body types and see what they are selling the most of. It should help.