Learn Finnish: Pesula on vuokraamon vieressä. - The laundromat is next to the rental shop.

It comes from the noun pesu (washing). By adding the suffix -la, it becomes a physical place for that activity. So, a place for washing is a laundromat.

Where does the word vuokraamo come from, and why does it use -mo instead of -la?

The suffix -mo or -mö is typically added to verb stems to create a place where that action happens. Here, it attaches to the stem of the verb vuokrata (to rent). Generally, -la and -lä attach to nouns, while -mo and -mö attach to verbs.

Why is it vuokraamon with an -n at the end?

It is in the genitive case because it comes right before the postposition vieressä (next to). In Finnish, most postpositions require the word connected to them to take the genitive -n ending.

Could we say pesula on vieressä vuokraamon instead?

No, because vieressä is a postposition, meaning it must come after the word it modifies. The standard word order is the genitive noun followed by the postposition: vuokraamon vieressä.