I feel bad for not telling my mom that im buying a house and moving out

For context im 27F and my mom is 59, sibling 30M with 3 kids.

My mom is under the impression that it will be easier for everyone if me and my brother live in the house after she dies and keep it up.

The problem...I DONT WANT TO LIVE THERE

My brother is a financial wreck and c an't afford rent, car and other necessities so my mom bails him out of his troubles a lot. He also doesn't respects people's property (taking things without asking and not returning or breaking them and not replacing) so him living with me is NOT something I want to do. I believe she has crippled him and he's used to her being a fall back.

Me, I'm financially stable with a good job, a good partner, and have received the clear to close on a house about 25 mins away. My mom told me before I didn't need to get a house until I finished with college and got a good job. Which after some years, I DID. NOOOW she's saying I'll be ready in a few more years and won't expand upon that.

I don't have a few more years. I want out of her basement ASAP and I feel like I can't tell her without a negative reaction.

Some clarity.. my mom has always responded negatively to the things I've wanted to do and she frames it as "keeping it real". If I wanted to work somewhere "you won't last long there" or "that's not a good decision you should work in an office (like her).

However, no matter how many times I've proven her wrong she always shows the negative "what ifs" to my decisions. Rarely positive encouragement. So I haven't told her I was buying a house in fear her pessimism would lead me to doubt myself.

I just feel bad that I couldn't and still can't share the process with her until it's over. And I don't know how to tell her even after I close. I really think she doesn't want to be left in the house with my brother who will surely tear it apart.