Normally, the idea of collecting classic cars is seen as a "rich people hobby." Understandably so, vintage vehicles tend to cost a pretty penny. But it's for this exact reason that German banks are recommending you use classic cars as an investment.

Germany is witnessing a booming gain on vintage cars. According to Bloomberg, a vintage Porsche 911 has gained 683 percent over their original value over the past 13 years. The local OTX classic car index, which measures the values of the top 20 most-valuable cars, increased four times over from 2005 to 2018.

While they aren't suggesting you drop all stocks in favor for an old school ride, many banks believe that a classic car would help develop a well-rounded investment portfolio. They also advise that you choose the right car at the right time. Financial experts estimate that a vehicle valued at $116,000 right now has the greatest potential.

Though like with all investments, it's a gamble. Things may change, and you could be out by thousands. Play it safe, folks.