Staying up to date on information and creating materials in this field is essential. I will will list a few site that I am familiar of to get the ball rolling. However, do not stop there always ALWAYS keep researching and educating yourself, especially in a field like this one.
Teachers pay teachers -
https://www.teacherspayteachers.com
I have yet to begin my career, but I did have the chance to intern in New Jersey's public school district for a few months with some amazing women who recommended this site for speech material. It can be very hard to develop your own games and worksheets for students, which is why this website exists! Teachers Pay Teachers contains cheap (and expensive) material created by other teachers that can be used to build a foundation of material for your clients.
Peachie Speechie - www.peachiespeechie.com/speech-apparel
If you are looking for a blog, shop, and materials all in one, this is the website for you. There are tons of cute shirts on this site as well as a lot of great advice and tips in the Blog section.