I want an ac, but getting one installed is so ridiculously expensive.

Maybe go for a Window Rattler instead? Easy to install.

Don’t you need those weird windows for that?

Might be a regional thing. Here in Australia our houses often have sliding windows, so it’s not hard to open one and mount an aircon in the space, sealing around thy edges.

I think some other countries use hinged windows which are less amenable to being violated by a Window Rattler. Placing the entire unit inside against the window and creating some improvised ducting for the outdoor air inlet side can also work in a pinch.