the 2nd is different meaning, I’m not sure what you would do to prepare for clothing but in no way does it imply getting dressed or buying clothing.

#2. I’m here on business.

Feels more natural.

I’m from the USA if that biases my answers.

Both “here for business” and “here on business” are acceptable, but “here on business” is a more natural idiom. I hope this helps!

Its time to go get your clothes; are you ready?

I’m here for business and I’m here on business are both fine. And they both sound natural, some peole would say ‘on’ and some would say ‘for’. Neither is more correct than the other

Second Question – Look at the question before you see the answer. Your question is “Why are you here?” Logical answer is “I am here for Business”.

If the same question is like, What are doing here?”. The answer shall sound “I am here on Business”.

The first answer is “reasoning” the presence of one at a location. But the second one addresses the happening.

I feel, The answers shall more situational and question dependant than looking at the logics.

Second, I personally would use #2 however, I think #1 is probably the more proper choice.

Also- Let’s go buy your clothes.

Let’s go shopping for clothes.

I’m here on business.

2. I’m here for business

you can say either on or for business but “for business” makes more sense

we will go,It’s time to get your clothes may be correct