Trying to build a business with a B2B app. While I'm building should I just get an LLC, and once I start making money switch to an S-Corp?

Let's assume it takes off and everything goes amazingly. In reality I'll be building it for the rest of this year. Maybe trying to get initial clients in 6 months. In this first year should I register an LLC or just go immediately to S-Corp. I'll have expenses, even if I'm not making money, this year is why I'm wondering. Thanks.

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