Les réparations locatives commencent avant la remise des clés.

In French, a plural countable noun usually needs an article. So les réparations locatives means the tenant-related repairs or the rental repairs.

French uses articles much more often than English does. Where English might say repairs begin..., French very naturally says les réparations commencent....

Locatives is the feminine plural form of the adjective locatif, which relates to renting or tenancy.

It agrees with réparations, which is:

• feminine
• plural

So:

• réparation → feminine singular
• réparations → feminine plural
• locatif → masculine singular
• locative → feminine singular
• locatifs → masculine plural
• locatives → feminine plural

In this sentence, réparations locatives is a set phrase often used in housing contexts for repairs that are the tenant’s responsibility.

Because the subject is Les réparations locatives, which is plural.

The verb commencer must agree with its subject:

• la réparation commence
• les réparations commencent

So commencent is the ils/elles form in the present tense.

Both structures can exist in French, but they do not mean exactly the same thing grammatically.

Here, avant la remise des clés uses a noun phrase:

• la remise = the handing over / delivery
• des clés = of the keys

So the structure is:

• avant + noun

If you say avant de remettre les clés, that uses a verb:

• avant de + infinitive

That would mean before handing over the keys.

The sentence you were given uses a more formal, administrative style, which is very common in legal, housing, or official language.

La remise is a noun from the verb remettre.

Here it means:

• the handover
• the delivery
• the handing over

So la remise des clés is a very common expression meaning the handover of the keys.

This is especially common in real estate, rentals, hotels, and administrative contexts.

Here, des does not mean some. It is the contraction of de + les.

Because la remise is followed by de + les clés, French combines them:

• de + les → des

So:

• la remise des clés = the handover of the keys

This is different from the partitive or indefinite des you may know from phrases like des pommes.

Because in French, the usual expression is les clés = the keys, even if in real life there may be one key or several.

In housing and rental contexts, keys are often thought of as a set, so plural is very common and idiomatic:

• la remise des clés
• la restitution des clés
• perdre ses clés

French often uses the plural here where English also commonly says the keys.

Yes. Avant can be followed by:

• a noun phrase: avant la remise des clés
• de + infinitive: avant de partir
• a clause, usually with que: avant que vous partiez

So avant la remise des clés is completely normal. It simply means before the handover of the keys.

A careful pronunciation would be approximately:

Lay ray-pah-rah-syon loh-kah-teev koh-mahn-sah-vah(n) ah-vahn lah ruh-meez day clay

A few helpful points:

• les sounds like lay
• réparations has a nasal ending in -tions
• locatives ends with a pronounced v sound before the silent -es
• commencent has a nasal vowel at the end; the final -ent is silent
• des clés sounds like day clay
• clés has a silent s

There is also a liaison in careful speech between commencent avant, so you may hear a z sound linking them:

• commencent-z-avant

Yes, it sounds fairly formal or administrative.

Two things make it sound formal:

• réparations locatives is a legal/property-management expression
• la remise des clés is a formal noun phrase often used in contracts, notices, and official communication

In everyday conversation, someone might say something simpler depending on context, but this sentence is very natural in written French about rentals or housing.