I have just really took an interest in climbing and I was wondering how long I should wait till I by a pair of shoes any help would be great.

To add to Ian's economic assessment of why buying shoes is a good idea, it's also nice to have your own pair of shoes that fits you well, and having your own shoes takes out the "ew" factor that comes with renting climbing shoes. I'll also agree that trying them on is an excellent idea - the fit of climbing shoes is a pretty precise thing, and is not necessairly related to shoe size at all. Poor fitting climbing shoes can lead to really really sore toes (more than usual...).

I started climbing a couple months ago and i bought my Evolv climbing shoes within weeks of starting to climb. It's very nice to have you own pair when climbing. If possible, try to get to an REI or local climbing gym and find a size thats right for you.

Liam, you need to offset the cost of buying shoes with renting shoes. If you're getting out once a week and it costs you, say, $7 to rent shoes, then in 12 weeks you've paide $84 to rent shoes. You can easily buy a pair for $84. If you're going more often, then you'll save money from renting even sooner. I'd say as soon as you find yourself making a habit of going to the climbing gym, buy some shoes. You won't regret it.