I want to buy an apartment pre-sale right worth 800 million KRW in 2029... How should I plan?

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I live in the provinces and have found an apartment I really want to move into, but move-in is scheduled for 2029.
The sale price is in the high 600 million to mid-700 million KRW range... but I expect it will go up to 800 million KRW in three years.
(Recently, new construction pre-sale rights have been inflating by at least 50 million KRW...)
My after-tax monthly income is 4.4 million KRW, and my annual pre-tax salary is 63 million KRW, though I'm not sure how much that will increase in a few years..
Recently, I took out a 50 million KRW first-time homebuyer Didimdol loan and bought a 200 million KRW apartment..
That is my entire net worth.
It seems like the Bogeumjari loan is only available for properties under 600 million KRW.
No matter how much I rack my brain... I don't feel like I can afford an apartment at that price.
How much cash should I have on hand..
I would like my monthly loan repayments to be less than 1.5 million KRW.
I don't think I can handle anything more than that..
I am seeing someone, but marriage? Uncertain.
Money? I'm still preparing for employment, so I don't seem to have any.
Family? Both parents are "dirt spoons" (low income), so there is absolutely no support coming my way.
No matter how I look at it... it seems impossible for me to get into that apartment, right? T_T