Is it a bad idea running 5 days a week?

No, it is a wonderful idea as long as you don't run too much if you are new to running. Just take it easy at first. Running has numerous health benefits and as long as you don't run too hard you should be fine. I run 6 to 7 days a week and I haven't been injured since about 2 and a half years ago. Make shure that you eat right, stretch and stay healthy. But most importantly, have fun on your runs and enjoy every minute of your runs. I encourage you to run. If you feel that 5 days is a little too much, start with 3 or 4 days a week. Have fun.