You are so correct that many people take their own real estate photos with their cell phones or DSLR. They aren't great, but many clients don't know the difference. That is the problem. It's hard to convince the client that professional photographs are a better representation of their business.  I think the key is to take photographs in a way that they can't, such as lighting, angle, composition or even produce videos. They have to be shown that professional photography will help them sell more homes and make more money and thus is a better value for them. Good luck.