Hello Wallygreens,
If you have a fear of heights the best thing would be to start off cleaning bungalows.
While you are doing that, ask a window cleaner near you if he would let you tag along for a while, that way you could practice going up ladders, while someone is footing them.
After a while you will get used to it, as I had the same problem. Now I go up ladders all the time.
Hope this helps at all.
Kind regards.