The plan is to get a small piece of land next to a beachside  and build some tiny houses for homestay business.  One unit would be where we will live.  Wife is a great cook so my potential customers gets a homestay package with home-made meals included.

Am looking for materials that can withstand the water vapour from the saltwater.  Rust is a big problem for seaside buildings.

Agreed.  It could be my second option now.  Already thinking of a different plot somewhere near small streams of fresh water instead of the beaches. Like those you can find in Janda Baik.  Lesser maintenance headache.

First you need to cut the spending and live within your means.

Most people have good income but trapped in debt. I did the same mistake when I was younger so now cutting down on my spending.

Second, avoid getting new debt (e.g. car loan, latest phone). I've read and watched over and over again a lot of people boosting about buying new 100-200K car to save on petrol or maintenance cost on current car.

Unker personally working towards settling my house loan before I reach 55. If you are debt free when retired you should be fine. Dont be like some people that take house loan until 65-70 years old. Crazy.