B.B.
I work in a medical spa where we do laser hair removal. I have also had treatments done on my underarms.
There are lots of different machines that are used for laser hair removal. We use a Sonata at my office. If you are a good candidate for the process and have a well-experienced tech, expect to need AT LEAST 5-8 treatments to get 85-90% hair reduction. Most patients really don't get 100% hair removal. It just doesn't happen. You will likely go in for treatments every 8 weeks or so, to treat all cycles of hair growth. Yes, it does hurt, especially if you are having your period, or right before, so keep that in mind during scheduling. We offer patients a topical numbing cream that they can apply to areas to be treated prior to treatment. Topical creams will help, so can taking Advil about 30 minutes before your appointment, but it is still going to hurt. Costs do vary quite a bit, based on location so do your research on that. Also, you mentioned this being a post-pregnancy "gift" to yourself. Are you done having kids? If you aren't, wait to have laser hair removal. I got my underarms done before I ever got pregnant and had almost no hair left. It all came back when I got pregnant. Hormonal changes can really impact your results, so just be aware of that from the beginning.
There are risks associated with any laser use. Discuss this with the doctor/technician who treats you.
Good luck with your decision.