If someone fosters kids, when they adopt can they loose foster assistance or get less foster assistance?

In some states and in some cases, stipends continue.

In most cases, no, the money stops at the time of the adoption.

Fostering isn't a business. If you're looking to make money, forget it. You'll spend much more than you get.

SMH.

Yes, the foster subsidy goes away after adoption.

However, most states offer an adoption subsidy but not all children are eligible for it. The main thing you would lose is the child care if the children are in day care.

You do still keep the state provided medical insurance.

I adopted 2 kids from foster care and receive a subsidy from the state.

depends on state law ... you'll have to ask your foster care support person or consult a local attorney

Once you adopt, the children are yours. You are no longer providing a service, you are parenting. You don't get stipends for parenting.