You can print "generic" vehicles without fear, but I don't know if you print an accurate rendition of a Ford or Chevy that you could legally sell it. Obviously, you can print them for your own use.
People are another matter, there is no "copyright" on people that I know of, so printing those would be fair game I expect.
3D printing for something the size of a 1:50 car or truck will take considerable time with most printers, probably several hours. Printing people would obviously be quicker.
The time/cost of 3D printing isn't the only issue, it's the hand painting that runs up the cost and time as well.