Long time away from bikes (since college - 1965 grad) but thinking of getting back in. Can't run due to shot knees and need some cardio. Investigating bikes on-line and at local shops. Not there yet, but also need opinions/advice on what else I'm in for in the way of equipment (expenditures). Helmet seems obvious. what else essential, desirable? Also any clues about one brand of somehting over another would be helpful.