To never have my sons believe that telling me anything about who they are naturally would cause me to reject them has been a life's goal. I set the bar low, I guess, but still too high for some. What a shame. If one of mine had come out, I would have just said, "Yeah, I know. So could you empty the dishwasher?"
Since I did not experience this, I will limit my advice, but as a Dad who raised boys, here's some minimal guidance:
You never make any move before you are on solid ground. Don't tell anyone anything or have any confrontations until you are completely covered. Never gamble that your plans will work out. They will not. Instead, have everything fall into place first. Have a job, already be moved out, already be independent, then tell the truth. Never out yourself when you are weak and vulnerable. You don't need family rejection and life struggle to survive multiplying on each other.
Try not to say anything that permanently closes the door on your side. Twenty years goes by, you are in your 40's, and your parents have changed a lot. When I was a child, my parents would make racist remarks and were staunch conservatives. Now, almost 60 years later, they have gay friends, black friends, atheist friends -- they are far more open minded. So, try to hold your anger and disappointment and leave things, despite them burning the bridge, open so they can come back and you have not offended them beyond your outing.
Taxes are easy. Turbo tax online. I have used it for over a decade. If you are young, have no stocks, no mortgage, etc, you can do your own taxes in about 20 minutes, and it is no longer hard. Do not fear this. This is a thing you can figure out by yourself.
Credit - get your own credit cards, then never use them. Anything in their name - you can just cut them up because that is their credit, not yours anyway.
Opening a bank account requires very little money. Just go ahead and do that.
Good luck, kid. Maybe they will surprise you. Remember that grief comes with disappointment. They should not be disappointed, but that is another discussion. Grieving will involve denial (You aren't gay! What are you trying to do! Stop telling us these things!).. .Then anger... (What is wrong with you? You GET OUT! WE HATE YOU! I WISH I NEVER HAD CHILDREN!). This will be the hardest phase. It will be the one where you think you are lost forever. But they may come to regret it if you keep your cool and remember the future holds many possibilities. Then bargaining. They will start to ask if you have tried this, or they heard about a priest that can help you, or what about this girl, she is so hot surely cannot resist her. Son, let's go to a whorehouse. I will show you Vegas and you will come around. Then depression. They will simply stop contacting you. Then, maybe, if they make it that far - they may actually just give up. Or they could backslide repeatedly into any of the other phases of grieving over and over again.
You will never get a perfect situation. You will always be dealing with back-handed comments or something, if your parents are as bad as you think they are at handling this sort of news. They will always act like you could be fixed, or you are going through one of your melodramas (they saw many when you were a teen). You'll probably never reach the promised land of liberal mom and dad hugging your lover and welcoming you both in and acting like it is just a thing people do and no big deal.
And I am sorry for that. We humans have not come that far yet.