How is it like to live in Helsinki?
What is it like to live in Helsinki?
How is living in Helsinki?
What are the differences between these three sentences and what is the common way to ask someone for their opinion about the city they live in?
How is it like to live in Helsinki?
What is it like to live in Helsinki?
How is living in Helsinki?
What are the differences between these three sentences and what is the common way to ask someone for their opinion about the city they live in?
Here are three ways to ask for information about living in Helsinki:
How is it to live in Helsinki?
What is it like to live in Helsinki?
How is living in Helsinki?
Note that using "How is it like" is usually not standard in English.
There is nothing in the question which necessitates the person being asked to be currently living in Helsinki or to have lived in Helsinki, although it would be generally assumed that they are or have.
A standard way to ask someone if they like living in their city is
Do you like living in (insert city's name)?