First, you need to look at what skills the jobs will really require. If they are looking for an experienced DBA, you're a long way from qualified. If the postings you're looking at are with SMBs looking for some general IT staff, then you can probably already handle most of their needs.
Database administration is a discipline all its own. It takes a long time to learn databases at that level, and that's probably not what you want to do. Most of the shops looking for someone experienced with Exchange and SQL Server are looking for someone who can handle basic installation, configuration and, most importantly, troubleshooting. You can learn those skills pretty easily by just playing around with the software and using Google and maybe a few books. As others have already recommended, a TechNet subscription will be helpful here. SQL Express will get you started nicely. Don't consider yourself ready until you've managed to break things a few times and figure out the fixes on your own. I strongly encourage you to get familiar with Exchange 2012 and PowerShell, even if the job descriptions don't mention them - they're the way things in the MSFT world are going, and you'd need to deal with them sooner or later.