Learn Finnish: Onko sinulla rahaa?

Raha means 'money', but here it is in the partitive case, which adds an -a to the end. In Finnish, when you say you 'have' an uncountable mass noun (like money, water, or time), it must be in the partitive case because you are talking about an indefinite amount of it.

Why does the sentence start with onko (is) to ask if someone 'has' something?

Finnish does not have a direct verb for 'to have'. Instead, it uses a structure that literally translates to 'on someone is something'. The word on means 'is'.

What does the -ko at the end of onko do?

It is a question particle. To turn a statement into a yes/no question in Finnish, you add -ko (or -kö) to the main verb and move it to the very front of the sentence.

Why is the word for 'you' written as sinulla?

This is because of the Finnish 'have' structure. To say 'you have', you literally say 'on you is'. The -lla ending on the word sinä (you) is a location ending that means 'on', making the word sinulla.