I have my own kevlar so I don't know how much $$ to rent. You'll need to google that. If you are going thru SS Marie there must be a rental place there.(In fact, even if you're not, there's probably still a rental place there)
Kevlars weigh about 50#, but it's not just about weight savings. Sportspals are like barges compared to the type of kevlar normally avail for rent. So., IMO, if you're doing a lot of paddling OR a lot of portaging, it will be worth the money.