Envelopes are one of the easiest things to make out of paper. Find a style you like and look for a template. Zoom out and trace the template so it's the size you want. (On a phone or computer screen)
I chose these 4 styles. (5 if you count the one with the hole.) Cut them out and trace them again on card stock or something to make your own template.
Make sure you keep track of which flap is folded first. I also wrote out dimensions for the paper to go inside them later on so I wouldn't have to do it again.
If you want to make it look like a bill, cut a hole and a small piece of tracing paper. Glue the tracing paper on the inside of the envelope. (Or use the clear material from an actual bill (: )
Next, cut pieces of paper or whatever you'd like to go in your envelope. I made money for one of mine, a bill, a resume paper and regular "love letter" pieces. Then, glue the flaps together carefully.
When they are dry, fold up the paper and stick it inside! You can tape, glue, wax seal, or make an envelope sealant if you want to be really authentic. (Comment for more details on these methods)
Voila! Plain white envelopes! Get creative and try different colors and sizes, or even decorating the envelopes. Oh and don't forget to draw on a stamp. :) Good luck!
I bought 20 cent paper at Michael's and went to town! The possibilities are endless :) these ones have confetti that likes to fall out- hence the paper clips!