Back before I had a dedicated server I ran this site and demo.mojoportal.com and joeaudette.com on a VPS. It had only 500 MB of RAM and it was doing all it could to run those sites and eventually it was not enough and Ibegan to have trouble. That amount of memory doesn't give enough headroom because it uses most of that just for basic running of IIS and SQLExpress. If you can get 1 GB or 2GB of RAM on the VPS it might work okay/pretty well. But with a basic VPS package with 500MB of RAM you really are not going to get better performance than shared hosting, what you get is more control of the server but it doesn't have enough resources to give high performance or handle lots of sites. If the package has less than 500MB of RAM it probably won't work well at all and the app pool will recycle continuously because there isn't enough memory available.
Hope it helps,