New York Times has just published an excellent buy versus rent calculator that every first time condo buyer should check out. It is simple to use and you can easily adjust the assumptions to your specific situation.
The calculator covers all key elements that should go into the purchase decision, including:
How long you expect to live in the place
What are your mortgage details (interest rate, length, down payment)
Estimated future inflation and home price appreciation
Your personal tax situation (single versus joint, your marginal tax rate)
Ongoing home maintenance, insurance and utility costs
After you adjust each lever to your own assumptions, the calculator tells you the monthly rent level below which renting is a better option.
Of course, buying your first condo is not just a dollars and cents decision. Times has a related article that suggest you ask yourself 5 question about your plans and lifestyle as part of your home buying decision.