Recipes.. Write your own or use others?

Hi everyone! I am relatively new to cake decorating (I have been doing it for family and myself for a few years now but in the last few months I have actually started charging for cakes and getting orders yay!) This will probably be the first of many questions I will have haha. My question for everyone is do you use recipes that you have written yourself or do you use someone elses? I am currently trying to branch out into writing some recipes but I have almost no knowledge of the science behind baking and I don’t know where to even begin. Up until this point I have found all of my recipes online and tested different ones until I found one I liked. I have gotten to the point where I can take a recipe and add something to it… for example I found a WONDERFUL recipe for white russian cupcakes but I felt it needed something extra so I added a “cream filling” in the middle. Is it “ok” to use other peoples recipes? I plan on eventually having a home based baking business and I think I would feel a little guilty if I did’t use my own recipes but I was wondering what the norm was on this? Also does anyone have any resources for information regarding baking science and recipe writing? Thanks so much!