In theory, it's a good idea but in practice I wouldn't spend more than $100 on ski gear that I'll never use. I picked up a combo set, lifevest, and rope/handle combo for like $50, 5-6 years ago. I have an old 67" Mapple MPD ski that I used to use and now let friends learn on but I think a wider ski would probably be better. I also have a cheapo wakeboard that I abandoned in favor of something better. Yes they all take up room but it is nice to have a collection of stuff that your friends can choose from....and wakeboards make great tables for your calipers, gloves, tools, etc. Not really sure how I'd adjust my fin without all the other stuff on my wall.
I'm all in favor of spending money to teach more people to get out on the lake and have fun with me but I'd never buy the stuff new unless it was on an extreme discount.