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1) Company is usually trying to push people that age into feeders, inside, or retirement.
2) With no seniority, you'd be doing the worst routes with industrial (OVER 70's).
3) You might not get the hours being at the bottom and you won't hit top rate for another 4 years
4) For medical reasons, I would highly doubt they'd even qualify your 30 days because of the higher risk of injury you are.
I applaud you for wanting to go through with this.
My 2 cents of advice would be to go deliver Amazon (more hours, less strenuous, working hard would lead to better quality routes and jobs)