Use of "i" before an infinitive

[Hendrik]

Helo Andrew, somehow your question slipped by unnoticed and unanswered for a whole day.

Let’s get to the core of the confusion: the infinitive by itself never has an i before it. It’s always the phrase before the infinitive that sometimes ends with it. I am afraid that I can’t give you a hard and fast rule telling you when to use an i and when not, so in the end you’ll pick it up phrase by phrase.

tl;dr: Prepositions are tricky

Maybe you’ll find this older thread on the same topic useful:

When to use and when not to use 'i ' as a preposition before a verbnoun

In the sentence "Would you be willing to bring something to drink with you?’ (ch. 10 level 2 N) ‘i’ is used before ‘yfed’. In the sentence “Would you be willing to wait for him?” the ‘i’ doesn’t appear before the verbnoun ‘aros’. I’m puzzled why it is used before one verbnoun and not the other. Is it just an optional thing?