First of all, I am very proud that you want to come out and are looking for advice about it! Support from parents is one of the most concerning of coming out, and what you're feeling is alright. That being said, unfortunately, rejection does happen, but there are ways that you can cope with that.
Before coming out, it's best to see if you can predict their reaction. Are they generally open and accepting about LGBT issues or not? Bringing up the topic casually may help, and seeing how they react. If it turns out that they are not supportive, then it's best not to come out, especially if you are financially dependent on them. Your safety is the most important, always.
If it does happen that you come out to them, and they are not accepting, what you do next depends on how severe the situation is. Are they kicking you out? Or are they simply refusing to acknowledge your identity? Different situations have different problems, but one way to prevent this is to prepare for the worst. You may want to pack a bag with all your essentials in it, save up some money and make sure you have a place to stay. Whether it be a friend or relative, make sure they are aware about the situation and are willing to house you for a while. Have someone that you trust with the situation, so if it does become the worst-case scenario, you still have a backup plan.
- Make sure to predict how they might react, if it's not good, don't come out.
- Have someone you trust about the situation, and willing to house you for awhile
- Pack a bag and save some money
- Most importantly, stay safe. Nothing is worth more than your safety
Unfortunately, it comes down to this most of the times with us LGBT people. You are strong, and you can go through this! I believe in you, good luck! :D