When do I get a bigger office and can employ more people?

In Game Dev Story the number of people is limited by the size of your office, so in the beginning you can only employ 4 people. At some point I was asked if I wanted to move into a bigger office and I'm now wondering what triggers it.

So, what do I have to do to get a bigger office?

Solution 1:

I'm now pretty sure that you get the 3rd office after you win 3 awards for your games. It was triggered for me immediately after the awards ceremony.

Solution 2:

I didn't pay attention on my first play-through, but on my second play-through, I noticed the following:

• Y3, M12, W3, I was offered the 2nd office for 6.5k. It allows for 6 employees.
• T10, M12, W3, I was offered the 3rd office for 25k. It allows for 8 employees.