Each state has different laws.
A parent, can claim you on their taxes... if you are licensed. If you take "cash" under the table, and are not licensed, they cannot claim you.
It takes a lot of research... what the laws and requirements are...
You also need to have or find online, "contracts" that stipulates your services and the parents need to sign off on that.
There are legalities to be aware of.
And have a "release of liability" as well.
If possible, watch friends kids... instead of stranger's kids... get experience that way and its more flexible.
Also, it is often expected that the babysitter is CPR certified etc.
You have to have/decide what ages you will watch? What routines/schedule the kids will have, food? Do you provide that or the parent. Do you have a place for a baby/toddler to nap? Is your home baby-safe and proofed? Will you "school" them or just be a babysitter?
From what hours? Full-day, all week, or part-time? Think of YOUR schedule and your own child's needs when you figure that out. And the amount of time you actually want to baby-sit, versus having time to yourself and just your kid(s). What will you charge if a parent is late in dropping off or picking up their kid?
What about days-off or holidays? Will you charge per hour or a flat monthly rate? How much per child? What about siblings? Or charge per age of the child?
How will you get various kids to nap? What time?
Will you accept sick kids?
How will you handle injured kids on your premises? First Aide certification?
Lots of details to think about... and research. Research online, and in your state agencies.
I used to babysit. I spent a LOT of time researching it and checking the legalities of it. And creating my own "contracts" and rules.
All the best,
Susan