To my knowledge as long as it's under 10yr old, 4 door, roadworthy etc.
I don't recall seeing any restrictions to engine size. Remember though you may have to get 4 large adults and luggage up a hill.
I can't use my i20 coz it's a 2 door, which is a bugger coz it runs at 5.6L/km
Note, my knowledge is not that vast so i stand (or sit, sitting's more comfortable) to be corrected.
Just beware that in the likely event you get some large/tall/overweight passengers then they will give you a hard time for the length of the ride, then more than likely slam the doors on exit AND possible rate you 1 STAR.
Dont forget they sometimes carry luggage and/or shopping.....
No Airport for you !
You will also be spending copious hours cramped in a small, unhealthy vehicle just trying to earn enough to pay for it .
See a few Mirages out there at 1193 cc (1.2L)- with only 2 pax and driver on board there would be quite a few GC areas such as Tallai and West Street Burleigh that would just plain scare me... (insert suitable phraseology here!)