Do you mention to customers ahead of time that there is a chance that the cake may not turn out for some reason? It may just not be a good cake day. Like just yesterday my buttercream did not want to stick to the cake for some reason. What if you could not deliver a cake that your happy with?
I am in the same boat. I will make my first wedding and my first stacked cake. I will have very slippery fillings, and Cream cheese icing. I am also very nervous. But I make this cake for my friend, and I did mentioned that I am nervous about that, and read some disaster stories here on CC. I told her, in case of disaster, I will run to a bakery, and she will have some cake on her wedding. She smiled, but maybe I gave her an uneasy feeling about my ability to make cakes. I wish I would not tell her this. I would probably not tell to a real customer.
The more times you make a recipe the more confident you'll be about the outcome of the final cake.
I wouldn't try out a brand new cake recipe, filling and icing on a paid order. Make a small one for your family's consumption first just to be sure you like it and that it works.
The recipes I use are all approved by my HD so I really can't just add another one in until I get their approval.
I think it's simpler to have a list of tried and true recipes.
As far as the potential for disaster and whether or not you should mention this to a paying client.....I think it wise to have some disclaimers in your contract about weather, site location, filling and icing choices etc. But, not wise to tell a client that you "aren't sure" how a particular cake will turn out. You need to sell yourself and be sure that your client has the utmost confidence in your abilities.
Good luck! It gets less stressful the longer you do it!
Stop stressing! I just did my first stacked and wedding cake, using cream cheese frosting for filling and covering, and it came out fine.
I did practice several times before the actual day.
This was my sister's wedding, so I was extra stressed!
You'll do fine if you practice.