As art has no correlation to the stock market, it means paintings can go up in value even when the market crashes, making it a good diversification for an investment portfolio. But it's not just about having enough money to invest and diversify.
Every artwork is unique, and the art market has ups and downs just like any other market. Since it’s difficult to determine an artwork’s true value — a lot depends on the artist’s reputation and on the economy as a whole - you should be comfortable assuming some risk.
The upside is: even if the value of an artwork does not go up in value in the short term, it's about enjoying the artwork and having the opportunity to pass it along to future generations. And, if a piece is rare, well-crafted, and well-preserved, chances are that it's monetary value will rise dramatically.