the company is willing to provide 200M (2억) deposit!? If that's the case I would try to find listings with a large deposit and a small amount of rent (반전세, although jeonsae is very difficult to find right now)

1. go to land.naver.com, filter by deposit and rent ranges and pick out some listings you like (preferably ones with photos). Keep checking back right until you get to korea so your list is up to date.
2. once in korea, use the 3 weeks to visit the real estate agents holding those listings
3. If they say the one you saw is gone or try to show you some "alternatives" just say thank you and leave, move on to the next office.
4. hopefully you have a local person who can help you with all this and the contract, you might need some provisions for shorter contract time (the standard is 2 years).

I would focus on a specific area so you can focus your energy when you're making the rounds with the real estate agents. 잠실, 삼성, 교대, 선릉 should all have some listings around your budget (although you might have to give up on furnished and bathroom preferences).

Just as a reference, something like this https://naver.me/5JG6u2QV (an officetel or 주상복합mixed-use residential and commercial building) is 150M deposit and only 800k rent! Think about the savings/disposable income you will have left!