As far as I know, you can wax the inside to make it as beautiful as you like but there is no need to wax the outside because you would want the hull to grip water rather than let water glide pass more easily. I have no idea about the cost of waxing though.
How long you need to WAX a boat depends on how "good" or how "shiney" you want it. In general, if you take care the boat yourself, I won't suggest you WAX always cos you would want to spend more time to play.
For take this to other to do, it depends on where, but I would share with you around 3k for a complete WAXing (multi layer).
What kind of you are having? May be a photo and I can share you some more info. You may also visit the upcoming boat show in Sai Hung this sat. There is some waxing stuff that you may want to have a look.