The cost of performing laser hair removal on your legs will vary depending on your size and hair growth. You can expect to pay anywhere from $200.00 to $400.00 per session. Most places will give a discount for purchasing package of various sessions. For example: lets say your price per session would be $300.00 you could buy a package of 6 sessions for $1,200.00 saving about $600.00 for the treatment. You should be able to split the price of the package in 3 or 4 payments and you should receive an extra discount for doing multiple areas (legs and private parts)
Contrary to what some laser centers will say, Laser hair removal is not permanent. The FDA classifies it as permanent hair reduction. The only way for it to be permanent is through Electroltsis but that is not a fun process. With that said, you can expect to have amazing results (I can go into detail of how it works if you like). After your initial treatments you would only need to perform maintance or touchup procedures once every year or two because of a few roque hairs that pop up every so often.
As for your skin getting uggly or staying the same. It will actually get better plus you will eliminate the problems of ingrown hairs.
One important thing to consider is the type of equipment your provider is using. Unless you have very light skin (white) stay away from anyone that uses an IPL for laser hair removal. IPL's are the old technology in the business which makes the procedure more painfull and can easily burn a patient. Stick to someone that uses either an Alexandrite or Yag laser, the yag being the safest one.
Hope this helps and if you have any other questions feel free to ask.