من الضروري أن يعاين المستأجر الشقة قبل أن يستأجرها.

من الضروري means it is necessary or it is essential.

A word-for-word translation is not very helpful here. The من is part of a very common Arabic expression used with adjectives like:

• من الضروري = it is necessary
• من المهم = it is important
• من الأفضل = it is better

So it is best to learn من الضروري أن... as a set phrase meaning it is necessary that... or it is necessary to....

In Arabic, the present-tense copula is usually omitted. So Arabic often says literally something like:

• من الضروري = necessary

  but in natural English we translate it as:

• it is necessary

If the sentence were in the past or future, Arabic would usually use a form of كان:

• كان من الضروري... = it was necessary...
• سيكون من الضروري... = it will be necessary...

Here أن introduces a subordinate clause. In English, depending on context, it can correspond to:

• that
• to

So من الضروري أن يعاين... can be understood as:

• It is necessary that the tenant inspect...
• It is necessary for the tenant to inspect...

This أن is extremely common after expressions like من الضروري, يجب, أريد, يمكن, and many others.

Because قبل أن is the normal way to say before [someone] does something.

Compare:

• قبل الاستئجار = before renting / before the rental
• قبل أن يستأجرها = before he rents it

So:

• قبل + noun / verbal noun
• قبل أن + imperfect verb

Both are possible in Arabic, but here the sentence uses the full verbal clause: before he rents it.

After أن, Arabic normally uses the imperfect verb.

That means:

• أن يعاين = to inspect / that he inspect
• أن يستأجر = to rent / that he rent

Arabic often uses أن + imperfect where English uses either:

• an infinitive: to inspect
• or a finite clause: that he inspect

So this structure is very normal.

Because أن causes the following imperfect verb to be منصوب (subjunctive).

In fully vowelled Arabic, you would see:

• يُعايِنَ
• يَسْتَأْجِرَ

instead of the indicative forms:

• يُعايِنُ
• يَسْتَأْجِرُ

In normal unvowelled writing, this difference is usually invisible, so the spelling looks the same.

Because Arabic often uses verb–subject–object order in verbal sentences.

So:

• يعاين المستأجر الشقة
  = literally inspects the tenant the apartment = the tenant inspects the apartment

This is completely normal Arabic word order. English prefers subject–verb–object, but Arabic very often places the verb first.

The subject is understood to be the same person: المستأجر.

So the sentence means:

• It is necessary that the tenant inspect the apartment before the tenant rents it.

Arabic often leaves out a repeated subject when it is already clear from context. You could make it explicit, but it would usually sound heavier than necessary.

No. يعاين is stronger and more specific than just see.

It means something like:

• inspect
• examine
• look over carefully

So in this sentence, it suggests that the tenant should not merely look at the apartment casually, but should check it carefully before renting it.

The ها is an attached object pronoun meaning it, referring back to الشقة.

Since شقة is a feminine noun in Arabic, the pronoun must also be feminine singular:

• الشقة = the apartment
• يستأجرها = he rents it

So the ها means it, but grammatically it is feminine because شقة is feminine.

• المستأجر is the subject of يعاين
• الشقة is the direct object

In fully vowelled Arabic, that would be:

• المستأجرُ = nominative, because it is the subject
• الشقةَ = accusative, because it is the object

You would also have:

• الضروريِّ after من, because it is in the genitive after a preposition

In normal Arabic writing, these short vowel endings are usually not written.

Because both nouns are definite in this sentence.

• المستأجر = the tenant
• الشقة = the apartment

In Arabic, a definite noun can sometimes be used generically, especially in formal language. So المستأجر may mean not just one specific tenant, but the tenant in general / any tenant in that situation.

That is similar to English sentences like:

• The tenant should read the contract carefully.

Here the tenant can mean tenants in general, not one identified person.

Yes. In English, both ways can work depending on style.

So this Arabic sentence could be rendered as:

• It is necessary that the tenant inspect the apartment before renting it.
• It is necessary for the tenant to inspect the apartment before renting it.

Arabic أن + imperfect often overlaps with both English patterns, so learners should not expect a perfect one-to-one match with a single English structure.