Ambiguity

It is difficult to make a judgement when the rest of the sentence is so odd, in particular the choice of simple present for the main verb.

1. Is #3 also confusing?

2. How could you correct the above sentences to convey the idea of "I find someone so that I prepare for it," "I find someone who prepare for it," and "I who prepare for it find someone" respectively? I hope you correct them as little as possible so that I can understand the structures.

lucas21cI find someone

That is odd and not very useful. Recast with I found someone or I'll find someone or I'm going to find someone or I've found someone. Those are all common, natural and useful forms of the verb.

If you want to remove ambiguity then you cannot just tinker with your sentences. You need to say something like:

I need to find someone who will make (the) preparations/prepare things.
I need to find someone so that I can make (the) preparations/prepare things.


I am not sure why you would need someone in order that you could make the preparations.

Does "I need to find John to prepare for throwing a party" sound okay?

No

lucas21cDoes "I need to find John to prepare for throwing a party" sound okay?

Is this what you mean?—

I need to find John to help prepare/throw a party.

Who helps throw a party?

To fivejedjon:

Could you tell me why?

lucas21cWho helps throw a party?

Presumably John, or you wouldn't need him.