To be a sleep walker you do not need to spend too much money. But, it will still be fun for your child. All you need is pajamas, and/or a bathroom. You can also use slippers to become more realistic.
If you want you can get a bit of baby powder. Slightly powder it on your face so you look tired and worn out. [do not get baby powder in eyes]. I hope this makes your Halloween and costume buying/making easier.
Thanks to an anonymous submitter for this easy idea!