Saving accumulation for property purchase strategy

Hi!

I'm planning to purchase a small 1br in LATAM for retirement (have citizenship there as well)

The prices are $50k-$100k CURRENTLY.

My plan is to buy a blueprint from a reputable developer so I can get better value and not have to pay all in cash one time (usually they want 30-40% deposit then resit with 2-3 years)

Not planning to take mortgage loan from there as rates are really high, my best option is a loan against my 401k, but I really want to minimize that loan as less as possible.

I have 6-8 months cash buffer already.

I don't have extra monthly saving so I was saving tax refunds for last 3 years and got around $18k saved.

Retirement is in around 15 years but I'd love to buy before that so hopefully in 5-7 years.

Initially I was planning to lock in 2 years CDs @ 4% APY then changed my mind to below:

What I thought is to put that $18k cash in a brokerage Fidel account with 100% VOO or VTI or maybe 80% VTI and 20% VXUS.

Hoping to get closer to $60-$70k with annual $6k-$7k contributions.

Of course I'm scared from market crash but plan is to wait it out of necessary and then if I reach my goal put the 40% down and switch to conservative investment like maybe a HYSE or CD for roaming 2-3 years.

Is this best strategy for what I described ?

Am I missing anything?

Do you have any suggestions?