We are truly sorry to hear about your financial struggles and your sister's critical health condition. We will stand with you in prayer and offer some biblical encouragement.
Firstly, it's important to remember that God cares about every aspect of our lives, including our financial needs and health concerns. His Word tells us to "be anxious for nothing, but in everything by prayer and supplication with thanksgiving let your requests be made known to God." (Philippians 4:6 WEB)
However, we must also remember that God's blessings are not always financial or material. Sometimes, He allows us to go through difficulties to draw us closer to Him. As it says in Romans 8:28 (WEB), "We know that all things work together for good for those who love God, to those who are called according to his purpose."
Regarding your sister, we are reminded that God is the ultimate healer. Even when doctors give no hope, God can intervene miraculously. As it says in Psalm 103:2-3 (WEB), "Praise Yahweh, my soul! Don’t forget all his benefits, who forgives all your sins, who heals all your diseases."
Let us pray together:
"Father in heaven, we come before You in Jesus' name, lifting up our brother/sister in their time of need. Lord, we ask for Your divine intervention in their financial struggles. Provide for their needs according to Your riches in glory. Help them to manage their finances wisely and trust in You always.
We also lift up their sister, who is battling stage 4 stomach cancer. Lord, You are the Great Physician. If it is Your will, bring complete healing to her body. Comfort her and give her peace that surpasses all understanding. Guide the doctors and caregivers, and be with the family during this difficult time.
Lastly, Lord, we pray that both of them would seek You first, knowing that You are able to do exceedingly abundantly above all that we ask or think, according to the power that works in us.
If either of them do not have a personal relationship with Jesus Christ, we pray that they would come to know Him as Lord and Savior. Remind them that it is only through Jesus that we have access to You, Father, and that there is no other name by which we can be saved.
In Jesus' name, we pray. Amen."
Regarding your request for a "big, quick, unexpected, financial blessing," we must be cautious. While God can certainly bless us financially, we should not focus solely on material wealth. Instead, we should seek God's kingdom first, and trust that He will provide for our needs (Matthew 6:33 WEB).
Lastly, we notice that Jesus Christ or His Name was not mentioned in the prayer request. It is only by His Name that we have access to God the Father. As it says in John 14:6 (WEB), "Jesus said to him, “I am the way, the truth, and the life. No one comes to the Father except through me." Therefore, we encourage you to come to Jesus Christ, believing in Him and trusting in His Name. It is only through Jesus Christ that God will hear your prayers and needs.