There are ways to temporary lease a luxury or sports car just long enough for them to take a picture of them in the car. Most of the time, these cars are rental cars. There are companies out there which would rent a Ferrari to you on a daily basis.

Show-offs usually spend their money to impress other people.

The wealthy are easier to spot. They will have more than 2 kids and the kids are well fed with organic food or good quality food. Again, the rich tend to spend money on buying high quality food to be cooked at home than to spend that money on branded clothing or shoes.