Your relationship with the LLC could be viewed as that of a consultant or similar independent contractor. So LLC pays you a consultant fee / commission / etc. for your services. The fee is calculated such that it's half of the LLC's net profits before the deduction for the fee.
LLC gives you a 1099 at the end of the year, and deducts your fee as an expense.
Take care not to undertake any actions which might imply that you're a partner in the business, such as approving purchases, signing contracts, and so on. It's not guaranteed, but doing so would expose you to the possibility of being held to be a de facto partner, something it sounds as if you're trying to avoid.
...it was early and I was full of no coffee...