I have no money to buy Visual Studio so I use the express edition
I want to use Microsoft ReportViewer
Is it legal to use ReportViewer without buying VS and how?
There is a Microsoft Report Viewer 2010 Redistributable Package
I'm unsure whether this means you can use it in visual studio, nor am I certain about the licensing.
I haven't used express edition for a little while. I'm guessing the control is in the download, you could try adding one of the dll's as a control.
I believe that you can use Reporting Services in SQL Server Express (which is free), which might indicate the validity of using ReportViewer in vs express.