This is a great idea, and I applaud you!
Just to throw in my own $.02, I cannot say enough about the quality of older, all-metal sewing machines. My vintage 1960s Kenmore may not have all the bells and whistles of the new digital machines, but it has a straight and zigzag stitch...which is more along the lines of what a beginning cosplayer needs. I'm sure that I'll acquire a fancier new machine eventually, but there hasn't been anything that I've been unable to do with my machine so far, and I've been sewing with it for around 5 years.
Also, older machines don't have the abundance of plastic parts of some of the newer models out there...the cost of fixing a broken part on a new machine may be higher than the cost of a new machine.
Next up: Dragoncon
Effie Trinket (reaping suit)
Irene Adler (pink bustle dress)
Team Awesome <333!!