My sister and her husband recently signed a document giving my husband and I temporary custody of her two children because they have a drug abuse problem and dss got involved.The document was notarized and is legal. My question is will we qualify for any financial assistance other than food stamps or medicaid to help with caring for these children (money for school fees, sports, clothing, etc... )

Just because it was notarized does not mean it was legal. It generally has to be ratified by a court. You should check with the DSS caseworker on this. ANY question on law needs to include your general locale as laws vary by area.

Assuming it is legal, you would probably not be eligible for anything you would not be eligible with your own children. Things like school fees and sports are luxuries, not necessities. Again, the DSS caseworker should be able to guide towards any resources available to foster parents (which is essentially what you are).

Check with DSS for options. If the agreement was through DSS you may have additional services they can provide or link you to. If it was an informal agreement, you may have fewer options.

Also, many jurisdictions will order the parents to pay you child support. Speak with a local family law attorney to find out your options.

Even if you get an award for child support, if the parents don't work it won't help. It will be like a check you can't cash.

Yes, I don't know why anyone things being notarized makes it become "legal" a notary is merely a formal witness. Does not really much more than your next door neighbor signing they witnessed you sign. Expect the notorary means they checked your ID before you signed and know it is you.

Unless the motion was filed with and though the court, or signed by a judge though ( CPS or what it is called in your state) the paper has no real "legal" status.

Next what assistance do you think you should get because you are baby sitting your sisters children, what you should get if they are doing court ordered custody to you, is child support from them.

Unless your income is so low to get food stamps, you don't get them automatically because of this.

And to be honest if you are so poor you are already on food stamps, I am not sure you need to be taking in sisters two kids

M My question is will we qualify for any financial assistance other than food stamps or medicaid to help with caring for these children (money for school fees, sports, clothing, etc....)

You have to go to the Court .There is a term "Kinship care" and some states and counties have Kinship Support Services Programs.
The main circumstance is the child to be placed in foster care .A relative who is caring for a child who is eligible for federal foster care receives a foster care payment each month.A relative who is caring for a child who is not eligible for federal foster care receives a welfare payment for the child./and this may mean food stamps or medicaid only /

.The document was notarized and is legal.
No way! Only a court order may grant you guardianship/kinship care.

many jurisdictions will order the parents to pay you child support.
Agree!
We do not know where the OP is located but here is one example:
Child Support requirements have to be met for the caregiver relative to be approved for Kinship Care. The caregiver relative caregiver is required to cooperate with Child Support staff to pursue child support from the parents provided that a good cause exception does not exist per 922 KAR 2:006, Section 16
If the relative caregiver is unwilling to pursue child support or sign the KC-01, Statement of Rights and Responsibilities, the caregiver relative is not to be considered for the Kinship Care Program. If the caregiver relative fails to cooperate with Child Support staff after approval, the Kinship Care funds are reduced by 25%.