I've been asked to come up with some ideas for low and no cost Halloween costumes for kids, mainly girls, but there are some ideas that will work for boys too. If you are stuck, last minute with little to no money for Halloween, hopefully, some of these ideas will work for you. There are many more ideas than this, but these are the ones I came up with.
A mummy - Simple. Rip up some old sheets and wrap them around your kid. I did this last year for me toddler and it worked very well.
A zombie. - Easy. Rip up some old clothes and slather some lipstick and dark eye makeup on their eyes.
Paper Doll - Simple. Draw some paper clothes on some paper, cut it out and tape it to your kid.
Mom or Dad. - Simple. Let them dress up in your clothes.
Clown - Easy. Let them dress up in mismatched colorful clothes and throw some extra lipstick on their mouth, cheeks and nose.
A Baby - Simple. Have them wear their PJs, preferebly feety one, and if you have a baby in the house, you can add a bib, pacifier, etc. Put in some pigtails and add a few freckles with some eyeliner
Nerd - Similar to the clown, but, add a few details...glasses with tape, slicked down hair, suspenders, if possible. And definitely hike up the pants as high as possible.
Cowboy or Farmer - throw on some jeans and plaid shirt. Overalls are best. If you have them, add a bandana and/or hat to top it off
Work-Related Costumes - Find anything from your job, or from those of people you know and have your kids dress up as a construction worker, teacher, mailman, etc using just a few borrowed touches.
Pop Star - Have your daughter find the "coolest" clothes in their wardrobe and add a few touches like sunglasses and bracelets. Maybe even a makeshift microphone.
Beauty Queen or Princess - Find your daughters nicest dress, curl her hair and throw on some makeup. You can make a tiara, if needed, out of cardboard and tinfoil.
Sports Related Costumes - If your kid plays any sports, it's simple, just dress them up in their uniform, or borrow one from a friend.
Well, those are all of my ideas. I hope some of them helped. If all else fails, you can go without a costume and say you're "normal"...the scariest thing of all =)