Time to get on my soap box for a moment.
In the past I've ran into instances where I disagree with others about what being a contractor means.
The belief I have ran into seems to be that it's 100% the responsibility of the company that you are working for to provide the tools you need. Now in some instances this is the case but in other cases it's common to just get Visual Studio. You can of course request other tools but depending on the process that could be a very quick or VERY long process.
Now personally I cannot live without Resharper, ViEmu, Visual SVN. When I go into an interview I make sure to verify that I will be able to have access to the tools that make me productive. My view is that if something as simple as installing software that increases my productivity to the company is going to be a pain then the rest of my time there is not likely to be pleasant.
So you're at your new job and it's time to start coding. This is where I and others come to a point of disagreement.
Personally I own a license for each and every tool I rely on. If a company I am contracting with has a license or for whatever reason wants to own a license for the tools I use then that's great. The day their purchasing process provides a license (or license server in the case of Resharper) I will gladly use it. But until that day comes I am perfectly happy to use my own licenses.
At the end of the day my belief comes from the fact that I view myself as my personal companies only product. And as such it's in my companies interest to make that product as useful to it's customers (in this case the company I am contracting with) as possible.
So whether it be buying tools and books or attending conferences I am perfectly happy to spend my personal companies money on it. It's all a part of improving the value of the product.
So with all that said.. If you use it.. Buy it! Why go without it for even a day? And if you have the tools you need you'll be better prepared if a side contract shows up in your lap.