@clayvaulin >i dont know about fireproof, but stick framing is pretty easy to learn.
I haven't done any stick framing, but I have made basic wooden joints before, so that's an option I guess.

I'm thinking I probably would want to make the walls out of concrete masonry bricks or similar (as it's ~$4 a brick and mortar seems cheap too), plus bricks are typically fireproof and I should be able to lay square enough walls after practicing enough.

I'd then probably want to make a wood framed roof, with corrugated steel as roofing, but I'd have to figure out how to make such roof without gaps, as I don't want flying sparks lighting the whole place up (as the bush tends to burn every few years).

>the bigger issue is plumbing, electrical and hvac
Plumbing seems very difficult, but achievable, as I can picture the processes of installing a septic tank, water tank, a pump and PVA piping and how working it all out should only take me "only" 100 hours.

As for electrical, batteries and solar seem to be finally efficient enough to be useful, but I'll need to calculate as to how much power I'll need and expected battery life (it'll clearly be easier to connect to the grid, but those power companies seem to use only the most proprietary power consumption measurement equipment with a mobile chipset inside (even them they seem to ignore the reported values and "estimate" power consumption instead if you use very little) and power is not cheap, so ehh).

With adequate insulation and suitable triple glazed windows, I should be comfortable with a fan and heater I reckon.

>an option to avoid fully building is to buy a serious fixer upper
Maybe that's a more realistic idea, but even those go for huge prices.