Learn Hardcore Russian: Аренда машины помогает путешествовать.

аренда машины = car rental / rental of a car (genitive, a noun–noun phrase)
арендую машину = I rent a car (accusative машину, with a verb)

Why do we use the noun аренда and not the verb арендовать (to rent)?

Both are possible, but the style changes.

Аренда машины помогает путешествовать.
Literally: The renting of a car helps (you) to travel.
Here аренда is a noun, giving a more abstract, general statement.

Using the verb would need a different structure to sound natural:

Арендовать машину — хороший способ путешествовать.
Renting a car is a good way to travel.
Если арендовать машину, легче путешествовать.
If you rent a car, it’s easier to travel.

The direct pattern *Арендовать машину помогает путешествовать sounds awkward in Russian; speakers would normally rephrase it as above.

Why is путешествовать in the infinitive form? Why not a finite verb like путешествуем?

After помогать / помочь, you usually use the infinitive to express help to do something:

Это помогает понять правило. – This helps (to) understand the rule.
Музыка помогает расслабиться. – Music helps (one) relax.

So:

Аренда машины помогает путешествовать.
= Car rental helps (one) to travel.

If you use a finite verb, you’d need a different sentence structure:

Аренда машины помогает нам, когда мы путешествуем.
Car rental helps us when we travel.

Why is there no explicit subject like “you” or “people” for путешествовать?

Russian often uses infinitives without an explicit subject to talk about general people or “one”:

Здесь трудно парковаться. – It’s hard to park here. (hard for anyone to park)
Легче учиться дома. – It’s easier to study at home.

Similarly:

Аренда машины помогает путешествовать.
= Renting a car helps (one/you/people) travel.

If you want to make the subject explicit, you can add a dative pronoun:

Аренда машины помогает нам путешествовать. – helps us travel
…помогает вам путешествовать. – helps you travel

Why is the aspect of путешествовать imperfective? Could we use a perfective verb?

Путешествовать is imperfective, used for:

general actions
repeated actions
processes without focus on completion

Here the meaning is general: traveling in general, not a single, one-off trip, so imperfective is correct.

A perfective like попутешествовать (to have a trip / to travel for a while) would sound odd in this sentence, because помогает also describes a general truth, not a specific event.

So:

Аренда машины помогает путешествовать. – OK (general habit / ability)
Аренда машины поможет попутешествовать. – possible, but now it’s about a concrete future situation: Renting a car will help (you) get some traveling done.

Does помогает agree with аренда somehow? Why is it not different for feminine?

In the present tense, 3rd person singular (он/она/оно) has one form for all genders:

он помогает – he helps
она помогает – she helps
оно помогает – it helps
аренда помогает – the rental helps

So помогает already fits аренда (feminine). There is no extra feminine ending to add.

Gender differences (masculine/feminine/neuter) show up in the past tense and in some adjectives, not in present-tense verb endings like this.

Can I change the word order, for example: Помогает путешествовать аренда машины?

Yes, you can change the word order, but the neutral, most natural order here is:

Аренда машины помогает путешествовать.

Other options:

Помогает путешествовать аренда машины. – possible, a bit more expressive, focusing on the “helping to travel” part first.
Аренда машины путешествовать помогает. – sounds awkward and unnatural.

Russian allows flexible word order, but certain orders sound more natural. For a simple, neutral sentence, keep:

[Subject] + [Verb] + [Infinitive]
Аренда машины помогает путешествовать.

Could I say Аренда машины помогает в путешествиях instead of …путешествовать? What’s the difference?

Yes, you can:

Аренда машины помогает в путешествиях.
Literally: Car rental helps (you) in travels / on trips.

Difference in nuance:

помогает путешествовать – focuses on the action of traveling; car rental makes it easier to travel.
помогает в путешествиях – focuses more on the situation of being on trips; car rental is helpful during trips.

Both are correct; your original sentence is a bit more direct and typical.

Could аренда машины also mean “car rental business / company”?

Yes, аренда машины (or more often аренда машин, аренда автомобилей) can mean:

the service of renting cars
sometimes even, by metonymy, the business that provides this service

Context decides:

Аренда машин в этом городе дорогая. – Car rental is expensive in this city.
Я работаю в аренде автомобилей. – I work in the car rental business.

In your sentence, it’s understood more generally: renting a car as a service that helps you travel.

Why are there no articles like “a” or “the” before аренда or машины?

Russian has no articles at all (no “a/an/the”). Their meanings are expressed by:

context
word order
sometimes pronouns or other words

So аренда машины can mean:

car rental
the car rental
a car rental

depending on context. In English we have to choose one; in Russian the phrase itself doesn’t mark this difference.

Is аренда машины the only natural way to say “car rental,” or can I say аренда автомобиля?

You can say both:

аренда машины – very common, conversational, neutral
аренда автомобиля – a bit more formal or technical (typical in ads, contracts, websites)

So your sentence could also be:

Аренда автомобиля помогает путешествовать.

The meaning is practically the same; only the level of formality/stylistic flavor changes slightly.