My dad thinks he's Bill friggin Gates and now, I'm no longer his babygirl

I (24F) am the youngest of four kids. I have a brother (32M) and 2 sisters (35F, 29F) (I, sadly, am the only one who went to college). 2 months ago my dad (57M) announced that he bought a house in one of the most exclusive professionals neighborhoods in our state. He claimed he paid it in cash, but he had no problem financing the new house with a 30 year mortgage (we're not US-based, so 30 years is the max period). <br><br>I just had to laugh at this, considering how little the man earns. He loved the rich guys, pretended to be one and he'd go on rants how to be a millionaire you just need to do xyz, and with his "educations" we'd be rich too. Honestly, my dad has a serious mental condition, it just hasn't been diagnosed but this is why I am not too harsh on him. He openly admitted that he just wanted to be Bill Gates, Elon Musk, and Jeff Bezos. He just wanted to be a money making machine. I will just call him "Bill" from now on. <br><br>He said we can't move in because it's "too hard" with his job as a driver and that he's going to finish the inside and exterior of the house. He claimed that he was going to take out another mortgage to finance the house and the "expensive" outside company he hired. I just felt like my dad lost it completely: you can't finish and furnish a house with a mortgage. I offered to help him with the finances (I work for a bank) and he threw a huge fit at me, yelling that I just wanted to be in control of his life. I never said that and I tried to calm him down, saying that I just wanted to help him, but he just got really really mad and didn't even let me see the "new house". He said that I wasn't his babygirl anymore because I didn't believe in him. <br><br>This weekend we had to go there for his birthday. He wanted to show off his "new home" and I couldn't not go because then I'd be in big trouble. The house was mostly empty with a few pieces of furniture. It was a big house, but it was in poor condition. The previous owners probably just cashed in, because there were a lot of things broken that needed attention. It looked like the inside of the house hadn't been touched at all. I never saw him so happy. When we were all there and he showed us around, he kept saying "Welcome to my house", like we were strangers visiting him. I felt like I was visiting a stranger, not my father. <br><br>I just don't know. I don't know how he thinks that he can pull it off. I know he's delusional, but this is something else. I just saw how happy he was and I was so worried that this would not end well. I just don't want him to get evicted from that house. <br><br>How would you handle this situation? I don't want to ruin my father's "dream" because I love him, but I think that he needs someone to intervene. A part of me just wants to let him fail and call it a day, but I know that this will never end well.<br><br>&#x200B;