These sentences mean the same thing! And they're both correct! :D

Yes, they do mean the same thing, but one comes across as slightly more positive than the other. "I'm not rich enough to buy a house" sounds a little more hopeful because it implies that you're likely on your way back up, whereas "I'm too poor to buy a house" sounds like little is going to change for the better.

I'm too poor to buy a house. I'm not rich enough to buy a house. They both mean the same if you are talking not having the financial resources to buy a house. But there are different if your listener want to interpret your financial well-being from these sentences. The first one emphasised on your poverty ( TOO poor, meaning you are poor all along), while the second just emphasised a lack of money now, not that you are poor or anything like that. So, the 2nd is best used when you can't afford anything. Poor is a negative word