moish, that’s a tough question. Definitely one of the greater challenges in life, for those who have oodles of money, is how to use it properly. Obviously it is a very high madreiga of avodas hashem for someone who has 10 million to burn to buy a simple house and give the rest to the needy/build public institutions. That doesn’t mean that someone who buys a 10 million house is wrong, necessarily, but it is a big test. Wealth is very challenging.
As far as not buying things because of Moshiach, I never understood the argument. If Moshiach comes tomorrow I will follow him and leave my brand new mansion behind, with no regrets. Material possessions are for the present life, and life after Moshiach comes is different. Why would buying things make me not want Moshiach? My money won’t be good after he comes, either (you can’t take it with you).
I think it comes down to using your money for your own gratification vs using it for mitzvos. If you want to enjoy the few days between your purchase and Moshiach, that in itself is not a lack of emunah.