Second Act, glad you found something you love doing!
For processing, reg. processors vs Square would depend on the ave amount you process monthly to determine which will be better for you. Since the business has always been cash, it will take time before people get accustomed to paying by CC.
Some businesses around here charge a fee for using a CC. They have a sign that says they prefer cash but for a convenience fee of 3% we will accept ..............
This is a recent change in law allowing the merchant to pass along the processing fees. I am not sure how the law works but think the establishment must post. You would need to ask your processor.
Best of luck to you! Cheers!.