wifi coverage large apartment

Hi,
what would experts recommand how to cover larger apartment (120 m2) with wifi when we know that modem with internet is in the corner (and have to be).
I assume wifi router connect in that corner. But on other side of appartmend could be no or bad signal.
So how to solve this?
- UTP cable to another side of appartment and another wifi router?
- Extender to receive wifi signal and create "new one"?
- power line?

I would prefer to have 1 SSID and smart switching between APs based on signal strenght

So what technical solution and hardware could be the best? And not expensive - just as home solution.