In order to write an introductory paragraph, you need to know what you are going to argue. You should not write your introductory paragraph until you have a good idea of the overall thrust of your paper.
On this topic, there are studies that argue both sides and you will need to decide what you believe. Some studies argue that hosting the games has a positive impact on a nation's economy. The argument is that the games attract so much tourism that they have a net beneficial impact.
On the other hand, there are studies that argue that Olympic Games do not really help a country's economy. Some studies argue that all the construction that is needed in order to host the games ends up costing more than the games are worth. The money is often spent on large sporting venues that never get used again. This waste negates the positive impacts on tourism.
So, in order to write your introduction, you need to decide which side you are going to take and then write a paragraph that briefly states this and also states the bare bones of what your argument will be.