Learn Hardcore Korean: sukbak giganeul yeonjangharyeomyeon chuga yogeumeul gyeoljehaeya haeyo. - If you want to extend the stay, you have to pay an extra fee.

-(으)려면 after a verb stem means “if you intend to/if you want to do X, (then) ….” It sets up a requirement or precondition for the intended action. So 연장하려면 = “if you want to extend / in order to extend (the stay).” It signals that what follows is needed before the extension can happen.

Can I just use -(으)면 instead of -(으)려면? What changes?

Yes, but the nuance shifts.

연장하려면, 추가 요금을 결제해야 해요. = To extend, you must pay an extra fee. (Requirement/precondition)
연장하면, 추가 요금을 결제해야 해요. = If you extend, you will have to pay an extra fee. (Consequence/result) Both are correct, but for rules/instructions, -(으)려면 feels more natural because it frames the fee as a requirement to proceed.

Could I say 연장하고 싶으면 instead of 연장하려면?

You can:

연장하고 싶으면, 추가 요금을 결제해야 해요. This literally means “If you want to extend, you have to pay….” It focuses on the speaker’s desire. -(으)려면 feels a bit more neutral and instruction-like; -고 싶으면 highlights personal desire. In notices or policy explanations, -(으)려면 is slightly more standard.

Why is 을 after 기간? Can it be dropped?

을/를 is the object marker. 연장하다 is transitive (“extend [something]”), so 숙박 기간 is marked as the object: 숙박 기간을 연장하다.

In casual speech, object markers can sometimes be omitted (especially when context is clear): 숙박 기간 연장하려면…. In writing or polite speech, keeping 을/를 is safer and clearer.

Why is there no subject like “you”? Is that normal?

Yes. Korean often drops subjects when they’re inferable from context. Here, it’s obviously about “you/the guest,” so it’s omitted. Adding 당신 is usually too direct. For polite, customer-facing language, you might see:

고객님께서는 숙박 기간을 연장하시려면 추가 요금을 결제하셔야 합니다.

What politeness level is this? Should I add -시 for respect?

-해요 style (as in 결제해야 해요) is polite but not the most formal.
Adding the honorific -시- shows respect to the customer: 연장하시려면 … 결제하셔야 ….
For formal notices, use -합니다: 연장하시려면 추가 요금을 결제하셔야 합니다.

What’s the difference between -아/어야 하다 and -아/어야 되다?

Both express obligation/necessity (“must, have to”).

-아/어야 하다: slightly more formal/literal (“ought to”).
-아/어야 되다: very common in conversation. Here, 결제해야 해요 and 결제해야 돼요 are both natural. Note the correct spelling 돼요 (not “되요”).

Why use 결제하다? How is it different from 내다, 지불하다, 납부하다, 계산하다?

결제하다: to settle/pay a bill, often card/online; businesslike and common for services.
내다: plain “to pay” (most general, colloquial).
지불하다: formal “to pay” (written/official tone).
납부하다: remit/pay dues/taxes/fees to an institution (very formal).
계산하다: to calculate/settle the bill (restaurants/cashier contexts). All of these can be used in specific contexts. In hotels, 추가 요금을 결제하다/내다 are most natural; 지불하다 is fine but formal.

What’s the nuance of 요금 vs 비용? And what about 추가금?

요금: a fee/fare/charge set by a service provider (phone bill, room charge, ticket fare).
비용: cost/expense in general (can include many components).
추가 요금: an extra fee/charge (most natural here).
추가금: “additional amount (of money)”—also used, but 추가 요금 is clearer for service fees. So stick with 추가 요금 for hotel-related charges.

Is the spacing correct? I sometimes see these written together.

Yes, the standard spacing is:

숙박 기간 (not “숙박기간” in formal writing, though the closed form appears on signs/ads)
추가 요금 (not “추가요금” in careful writing)
결제하다 is one word (Sino-Korean noun+하다 compounds are typically closed). Both spaced and closed forms for the noun-noun pairs are seen informally, but the spaced versions are preferred in standard writing.

Can I rearrange the word order?

Korean allows flexibility, but keep the condition before the result and don’t break tight units. Natural variants:

숙박 기간을 연장하려면, 추가 요금을 결제해야 해요. (original)
숙박 기간 연장을 원하시면, 추가 요금 결제가 필요해요. (uses nouns)
연장을 원하시면, 추가 요금을 결제하셔야 합니다. (honorific + formal) Avoid odd reorders like moving 추가 요금을 before 연장하려면 in a way that splits the condition unnaturally.

Pronunciation tips for this sentence?

숙박: [숙빡] (tensification: ㅂ becomes tense after final ㄱ)
결제: [결쩨] (ㄹ before ㅈ/ㅉ causes tensing)
해야 해요: [해야 해요] (often flows together in speech) A full, smooth reading: [숙빡 기간을 연장하려면 추가 요금을 결쩨해야 해요].

What’s the difference between 연장하다, 연장되다, 연기하다, and 늘리다?

연장하다 (transitive): to extend something (you do the extending) — fits here: 숙박 기간을 연장하다.
연장되다 (intransitive/passive): to be extended — 숙박 기간이 연장됐어요.
연기하다: to postpone/delay to a later time (not lengthen) — used for events, appointments.
늘리다: to increase something (broad increase, not just time periods). For hotel stays, 연장하다 is the idiomatic choice.

Why is it 요금을 결제해야 해요 and not 요금은 결제해야 해요?

Both are grammatical, but:

요금을 marks it as the direct object (neutral).
요금은 topicalizes it (“As for the extra fee, you must pay it”), which can sound contrastive or expository. In a simple instruction, 요금을 is more straightforward.

Can I say 결제를 해야 해요 instead of 결제해야 해요?

Yes. Both are natural:

결제해야 해요 (verb form)
결제를 해야 해요 (noun + object + 하다) No real difference in meaning; the version without the extra object marker is a bit leaner.