Shooting headshots - or need to?  It’s nowhere near as hard - nor as expensive - as you think to get great results.
   You need only things that you have - or need to have - anyhow: a good camera, a good zoom lens, a sturdy tripod, either a ring light for macros or a good flash with diffuser, and a remote control for the camera.  The only thing you may need to buy is a background - and that’s quite inexpensive, given what does just fine.  And the cost of any of these things that you don’t yet have is probably less than paying someone else to shoot your headshot - plus, of course, you can use it over and over for many things, not only headshots.
   For a great - but inexpensive - background, you can’t beat foamboard!  Office Depot sells one which has a dark blue background on one side - and light blue on the other.  But - for most all uses - ordinary white foamboard that sells just under $3.00 at Wal-Mart is great.  The dark/light blue one is needed only if your subject wants that background - or wants to wear some outfit that won’t contrast with white, or has unusual complexion.  A sturdy clasp lets you easily hang it from a nail positioning it at a height most all people will fit.   Foamboard will stay perfectly flat - and will avoid having every paintbrush stroke on the wall conspicuously show in each photo!
   The subject - if male or transgendered - really does need to shave immediately before the session; believe me, every whisker will show otherwise!  Blouse or shirt ideally dark with pattern if the background will be white.
   Pose the subject in front of the foamboard with the subject’s feet at a slight angle to the camera - and with the subject facing the camera at a slight angle; this will make her look thinner.  Experiment with her tilting her head slightly up or down; down usually works best.  This also avoids the “mug shot” look.
   Ideally, the face and hair will fill most all of the frame - with a slight bit of the blouse or shirt below.
   Light should be either a flash with diffuser bounced off ceiling - or a ring light of the type used for macros.  Keep in mind that ring lights powered with “AAA” batteries will dim rather fast.  Avoid ring lights with AC adapters - to avoid tripping over your gear!
   Remotes for at least some dSLRs are best the radio kind - not the infrared ones - as the infrared kind will require adjusting the camera settings before and after for at least some dSLRs.
   It’s best to shoot headshots indoors - because that way you and your subject stay comfortable.
   Plan on taking many poses - especially if you’re both the subject and the shooter!
   
   

Shot with Canon 7D, Canon 24-70 f/2.8 “L” USM zoom lens, ring light, tripod, remote.