This is the 228th most frequent Finnish word.
liian
"Liian" means "too" (as in excessively).
In this sentence, 'liian' is used to indicate excessiveness, showing that the coffee is excessively hot to be safely consumed.
Tämä kahvi on liian kuuma juotavaksi.
This coffee is too hot to drink.
Here, 'liian' modifies an adverb ('nopeasti') to describe that the speed of speaking is excessive to a degree that comprehension was hindered.
Hän puhui liian nopeasti, joten en ymmärtänyt häntä.
He spoke too quickly, so I didn't understand him.
In this case, 'liian' emphasizes that the cost of the house is excessive, beyond what is appropriate or affordable.