Atmel Studio is entirely free and based on Visual Studio 2010
1) Can you join the free Microsoft Bizspark offer?
I don't know if you are planning a start-up business for your resulting project but if so then maybe this is way to get Vs Pro. I am no expert but as ling at you are in startup mode and/or your new business is less than 5 years old and turning over less than $1m you might well get approved for Microsoft Biz Spark.
Oh and for your planning/startup you can buy a domain name for a few dollars per year which is very handy for professional email correspondence with suppliers :D
2014.04 - The following is a snippet from the faq shown above ...
Eligible startups must be:
Actively engaged in development of a software-based product or service that will form a core piece of its current or intended business*. To meet this requirement the software must:
Add significant and primary functionality to the integrated Microsoft software.
Be owned, not licensed by the Startup.
In business for less than 5 years, and
Bringing in less than US$1 million in annual revenue
Microsoft may permit individual developers or others and/or separate technology entities who may not meet the standard eligibility requirements to join BizSpark from time to time.
 Startups who are actively engaged in software development but have not yet completed the formalities of establishing a business.
 This requirement has been adjusted to add local variances calibrated to local economic conditions in the startup’s place of business, below. If a startup's place of business is not listed below, then the revenue limit is US $1 million. US$750,000 China, US$500,000 Korea, Malaysia, Poland, Russia, Spain, Ukraine US$250,000 Egypt, Thailand, Turkey, and Vietnam
* Not eligible for BizSpark
If you are developing dashboards, HTML editors, utilities, website, and similar technologies that are not considered primary service or application.
If you are a consultant