Filing Fee for Affidavit of heirship?

I am the son of the deceased party and one of seven other siblings who are no longer interested in the property. I currently live on the property of my mother who deceased on Aug 19, 2010. There is no written Will for me or any of my family members to take over ownership as the Executor on the Estate of my mother Robbie Lee Sheffield. My intention is to make myself the Executor in agreement with my siblings to assume the payments and save the home from being foreclosed. I have presently unable to make payments to my mother's mortgage account and Bank of America will hire legal help to foreclose on the property unless I can provide probate court documents stating that I am the Executor of the Estate. Please advise me of the legal steps needed for me to rightfully claim full responsibility of my mother's Estate.