Made the same mistake when i started out last year ... i'd say definately go the hire route .. you usually then get the option to buy it if you want anyway , so a good way to go without having to commit to the long term costs until you decide its the sport for you . I just did the one event in the surf suit ... was about fifth from last out of the water .. of those behind me two others were in the wrong suits and one had decided to swim the whole thing butterfly.. The difference swimming in a propper wet suit is massive , will literally knock minutes not seconds off your time as you wont be dragging gallons of water with you, plus as mentioned above the bouyancy is set up to hold you in a better position.