Personally, I think a dslr camera is a waste for on line advertising pics.
There are many point and shoots that will take good photos for posting in a web site.
Look at pics posted on the threads here and try to tell which ones are taken with dslr or p&s.
Learning what makes a photo good is more important and you'll be able to accomplish that with a good p&s. I would look for one that has a hot shoe for a flash and make sure it has a tripod socket.