The Aprilla is more expensive to service, buy parts for and to run. If you want a fast 125 go for an nsr125.
Not really, parts aren't overly expensive and freely available compared to a NSR.
People saying they are unreliable are wrong. If you keep it in good nick it will be fine.
I personally wouldn't buy one though, after being in the same situation. I've currently got a RS125 being worked on, by myself. Kind of a 'project' to me. Should be on the road soon. If i was you I would use the money to get the test THEN buy a bigger bike.