Recommended Starter Instrument Guide
Pianos (Keyboards):
Search Casio or Yamaha brands and touch sensitive and 61 keys for smaller and cheaper options.  These are usually $130-180.  
Change to 88 weighted keys for a piano like feel.  These are usually $450-950.
Guitars:
4th or 5th grade and younger can get a three fourths size guitar, whether electric or acoustic.  
Older students can start with a full-size guitar.
For Acoustic, Acoustic Electric, or Electric Homestyle Music recommends Yamaha and Ibanez for brands.  If you are unsure, we suggest an Acoustic Electric, combining the best of both worlds.
All Winds (Flute, Clarinet, Saxophone, Trumpet, Trombone, etc.):
A cheaper brand that is not great but is functional is Eastar.  These are good as a starting point.  They can be a bit hit or miss but an understandable purchase for a young beginner
The better brands student and intermediate levels models for flute is Gemeinhardt or Yamaha. Yamaha is good for just about any wind instrument regardless of the level of the instrument.
Strings (Violin, Viola, Cello, etc.):
Yamaha is great, but Eastar offers functional starter instruments (though they may go out of tune more easily).