Our windows have cold air coming through them. I'm reaching out to see if there are low budget ways or hacks to make the windows more insulated. The windows are smaller and single-paned. Any tips or hacks are appreciated, thank you!
When I lived in a cold and draughty apartment, we put sheets of polythene across the windows.
The windows had wood frames. First we put up the polythene (on the inside) and secured it with drawing pins. Then we sealed the edges with masking tape.
Very cheap and effective "double glazing". Not only did it cut the draughts, it also prevented the air in the rooms having direct contact with the cold glass.
It made the glass a bit opaque, but it was only a street view anyway.
If it is your house (e.g. not a rented apartment or house), then you could (carefully) remove the wood trim around a window. See if there is silicone caulk around the wood frame of the window itself. You might want to check just the trim on one side of a window rather than pull all four sides off, at least on your test case.
I've seen cases where there is no caulk, and it allows a draft through that space.
The downside is that you have to be cautious not to damage the trim, and then put it back on after the caulking. But the only cost would be the caulk, which is pretty cheap. If your test window is nicely sealed, then I would not do this on any other windows.