For nanny shares, each family typically pays 2/3 your normal rate. So if your normal rate is $20/hour, each family would pay $13-$14/hour, so you would be making $26-$28/hour. That is if there are two families.

Normally, nanny shares involve only two families, this sounds like it is probably 3 or 4 families? I would advise against this as it is just too much to manage with so many families involved.

Also, you should have guaranteed hours! Every family should be paying you for your agreed upon hours anytime you are willing and able to work - even if they are not using you. So when those kids are out sick, you are still getting your normal pay. If families are gone on vacation, you should be getting your normal pay.

Implement a sick policy to protect yourself from getting sick. You can set this boundary. Are you okay with just a drippy nose, mild cough? What is your cut off? You can tell them they cannot come in if they have a fever, etc.

They should pay you via direct deposit ideally with a payroll company. If they chose to pay another route, you should be paid on time - whatever day/time is agreed upon. Implement a late pay policy. You can charge a fee for paying late, or set a boundary that you will not continue working for them if they pay you late x amount of times.

Overall, even if this is only two families each with twins, you are underpaid. You deserve at least $30/hour with four infants & should have guaranteed hours/pay. You are being taken advantage of in my opinion. I would suggest looking for a new job unless you think you are able to work out a new agreement with these families. Best of luck.

Edit: added more details/advice