1999 Volkswagen Beetle Won't start

My car displayed the "Check engine" light every single day that I turned it on. My friend that has a VW too said that these cars always display that. It was dumb to listen to her, because I went out this morning to start my car and absolutely nothing. No clicks, nothing. I turned it all the way. Auto zone used a little computer thing on my car, and it said failed Solenoid or something close to that. I also had my friend connect jump cables to my car, and it barely turned on. But at least I know my car can still work, if that even counts. So it might be something with the battery instead. I don't know. Either way. What is really the problem and how much will it cost to fix it? I'm really on a budget. Lol