Probably worth just talking to the school about it; if you buy the Sling you'll have to talk to them anyway in order to set up the lease. If it was actually capable of earning more profit than the Cessna/Piper options and paying back the initial outlay, they probably would have bought one already - so why haven't they?
The obvious limitations of the Sling 2 are that it's only a 2-seater (can't take a couple of mates on a flight) and it's pretty light (the heavier Warriors and 172s are likely to give you better experience for moving on to larger commercial aircraft, if that's where you want to go). Rather than comparing it to a Warrior or 172, a Cessna 152 might be a more appropriate alternative.
Apart from that, I've been told very firmly "do not do training in your own plane, and don't let anyone else do training in your own plane". Too much risk of breaking something, and insurance premiums reflect that.