What would you consider a fair price range for a "like new" (lightly used, well maintained, ready to sail) 1999 Hobie 17 Sport with trailer?
Like everything - it depends.
One man's idea of "well maintained" is another man's piece of junk.
Stored in a garage? Or left in the sun (and snow)? What's the trampoline like? What kind of rudders does it have?
What's the trailer condition? Gavlanized or painted steel or aluminum? All the lights work? What's the size / condition of the tires?
If the boat still has the original main sail, it's probably close to delaminating if it's not already.
Going on the assumption there are no significant issues, like leaking wing tubes or soft spots and sight unseen, the boat is probably worth $3500 or less. Trailer is probably worth $250 (steel), $350 (galvanized) or $500+ (aluminum). Aluminum trailers need to be thoroughly inspected for fatigue cracks.
To really make an estimate, though - we need photos (more the better).