Learn Finnish: Tuo auto on halpa, koska se on vanha. - That car is cheap because it is old.

In Finnish, you usually must put a comma before a conjunction that starts a new clause (a part of the sentence with its own subject and verb) like koska (because) or mutta (but). The word ja (and) is an exception and normally does not get a comma.

Why does the sentence use both tuo and se?

Tuo means 'that' and is used to point out a specific car (tuo auto = that car). In the second half of the sentence, se means 'it' and simply refers back to the car we just mentioned so we don't have to repeat the word auto.

Does adding koska change the word order in the second half of the sentence?

No, the word order stays exactly the same as a normal sentence. After koska, you just use the standard subject-verb-adjective order: se on vanha (it is old).

Why are the adjectives halpa and vanha in their basic forms here?

In Finnish, adjectives must match the form of the noun they describe. Because the car (auto and se) is the subject of the sentence and is in the basic form, the adjectives halpa (cheap) and vanha (old) stay in their basic dictionary forms too.