So was wondering what is good to buy for first windsurfer and how much should I expect to pay second hand. Also where is best place to buy. Also will my first board be lighter than what they teach you on, because that seemed kind of huge. Thanks.

Once you have the basics, you can go smaller than the big beginners board that would have been about 180 - 210L ish
You could do 130L freeride and uphaul that easily - except for the fact that no centreboard will make it drift downwind and be frustrating at first.
See if you can get a try of something like that with a small wavesail and see how you go?

As for cost, the free sails on the WA thread look great, you could get a quiver of 3 sails free, mast and boom say$400 and a 10 y/o freeride board for $300 is not hard to find