How to remove the musty smell out of the house?

spray and wash down everything with white cleaning vinegar mixed equally with water

You can mix fabric softener with water in a spray bottle. Spray the house and open windows when you can.

I find if you put some coffee grounds, baking soda, and if you want to a couple drops of essential oil, mixed in a coffee filter, tie it up so it doesn't spill and set a few around your place and it will help soak up any musty smell

The vinegar will help deodorize and kill any mold or mildew spores that may come from the dampness of the humidity in your house. Virgie's idea definitely a good one. Once the vinegar dries you won't smell it anymore and you can do the sniff test to see if some areas need a little more spray.

Activated charcoal. Place bowls of it in every room and closet. I would even go so far as to place in dresser drawers. Boxes of baking soda help too. Since you can't afford a dehumidifier, run portable fans. Borrow from friends or buy up whatever is left on end of season sale. Moving the air is what you need to do. If cool enough, open windows and doors.

I know you said about the dehumidifier but that's going to really help. Check with your local Nextdoor online community to see if someone is giving one away or selling, or even at a Habitat Store, Thrift Store, or Goodwill. Hope this helps. Hugs, Holly