Multiple Virtual Machines

I am looking to create multiple virtual machines. These will be used for social media/google accounts/ ebay/amazon/ etc. Probably in the neighborhood of 500 vm's.
I'm not a geek so these may be some basic questions:

Is this reasonable and what should I remember when creating them in terms of allocating memory? I only need them to log in to various accounts, not do actual work while running them.
Should I use a vpn service or proxies..another cheaper option?
What you recommend for OS for…

Multiple Virtual Machines