I have had laser treatment done on my upper lip . Whatever has been said above is all true..the contrast between the skin and hair color needs to be higher for the lasers to be more effective. However there are many more types of lasers now available and if you take a consultation from a doctor they will be able to guide you to what will work best with your needs.
Another suggestion is please go to a place which has at least one MD.
To answer your questions from my experience:
1. I took 6 sessions but will need at least 6 more since I have dark skin/dark hair plus i wasnt able to finish my previous sessions regularly.
2. 3 - 4 weeks which is equivalent to the hair growth cycle. Since all hair dont grow at once you need multiple sessions to cover as many follicles as possible.
3. yes. if you do it within the recommended period the chances of making sure all hair is gone is higher. I wasnt able to make each session in the 4 week time span resulting in regrowth.
4. Its upto you. If you pay up front they usually provide a 10-20% discount. I tried the first session at full price and based on the results decided to pay up for the remaining 5 together. My total cost was around $1200. I think I got a $25 /session discount.
5. I would have pain (its more like pin pricks) during the procedure and afterwards for about an hour or so. I used to apply aloe vera gel since the pain is mostly the stinging caused by the high temperature of the laser which raises skin temperature in the area and the gel had proved very effective in cooling.
The cream that someone mentioned above which is applied before the treatment also helps. I did not try it but my friend did and she had a painless experience. Also she has better results than me mostly because her skin is much lighter than mine.
Its been a year since my last appointment and overall my experience is positive. The hair has become lighter and sparse. I do need to remove them once every while. But once I manage to get the remaining sessions done I'm hoping it would be long term.
Hope that helps