Make sure you have plenty of cash to start with and be prepared to lose everything.
Working for yourself can be very satisfying, and you'll never want to work for anyone else.
You'll probably work longer than you've ever worked, for less than you've ever earnt - but ultimately if it all works out, you could reap the rewards.
The bike business is incredibly fickle. I've seen 7-8 shops open and close in my locality in 7-8 years. Only the very good and the big remain!
I started a shop 8 years ago with £7000 and 12 months later I went bankrupt for 5 times that!! What I should have started with was £40,000 min - but the temptation to own my own shop was too great and I rushed into it, made some bad decisions and have pretty much paid for it ever since.
However, my mechanic took over the workshop area (for 10% of the rent I was paying) and he's created a great little business and has a first class reputation - but it has taken over his life and he spent the first 5 years telling me on a weekly basis how he wanted to quit. Now he's established though and has recently expanded.
I definately want to have my own business again one day, but will use my previous experience to ensure I don't feck it all up again!
Good luck, I hope it works for you.