It's hard to say it varies by area so much it's hard to put a number on it. Entry level Linux jobs in my area are just above the burger flippers for salary.
My advice
Make sure your friends, neighbors, family, etc know what kind of job you are looking for. My current job was found through my neighbor.
If you want a Linux job make sure you have linux on your resume. The last place I worked for was looking for a linux guy and 90% of the resumes never even mentioned they knew unix or linux. The first thing the boss did was look for linux and if it wasn't on the resume he put it in the round file.
Back to my comment about linux guys just above burger flippers... My first job was a helpdesk supporting Fuel stops that were running on Unix I didn't make a lot of $ but I learned a ton about Unix. I worked there a few years and was able to get a decent job a few years later with the experience.
As for the certification portion I found that having a degree helps more with the $ than certifications. The certification helps when you both have the degree and you have a certification and the other guy doesn't.
Hope that helps.
