Realistic Golf Goals

I know it's different for everyone but what is a realistic goal for someone dedicated to improving and playing multiple times a week?

What is the gap between the best amateur player you're likely to be paired with and a pro?

I imagine it's harder to cut strokes the lower handicap you are but if you are a 0 handicap as a casual golfer what would it take to get down to a +4 to +6 and actually compete professionally?

Say I wanted to compete in pro-circuits outside the PGA, not necessarily to win money but to compete at the highest level possible what would I have to do?

Background, I was an amateur motorcycle racer on the verge of qualifying for pro races before getting taken out and forced into early retirement. I picked up golf and would like to compete in some sport at a "pro" level in my life time. I'm 41.