A driver with placards for both Lyft and Uber waits for a traffic light outside South Station in Boston.

The online ads sound pretty great. A guaranteed $2,500 monthly to drive for Lyft or $2,100 monthly for Uber, which is close to $30,000 yearly for what is a part-time job for many.

But here comes the bad news. First, there's lots of fine print to contend with that makes the offers not as swell. Second, a new study out Tuesday shows that drivers are, in fact, making way less than they were four years ago.

More people are on the roads driving for Uber and Lyft, and with "the rapid growth in the number of drivers has come a steady decline in average monthly earnings," says J.P. Morgan Chase & Co. Institute.

Earnings for those in the online transportation field fell 53% between 2013 and 2017, Chase says, averaging $783 per month in 2017 versus $1,469 in 2013.

That, of course, is a far cry from $2,500 monthly.

To get to $2,500, Lyft says drivers will make at least $625 weekly, and if they don't pull it in from fares, Lyft will make up the difference.

The requirements are that you need to start work at 5 a.m., accept 90% of the available rides, drive at least 30 hours a week, for at least 65 rides.

For Uber, the ride-hailing company notes that the $2,100 applies only to the first 200 trips, and that future earnings "aren't guaranteed." The 200 trips must be completed within 90 days. And the guarantee is for total earnings minus Uber fees.

Meanwhile DoorDash, the food delivery service, says drivers can make $1,750, but that's over two months and with the delivery of 60 meals. As Rideshareapps.com points out, drivers are also responsible for gas expenses, maintenance and taxes.

"Notes Rideshareapps.com: The DoorDash website claims drivers can make up to $25/hour, which might be a stretch for most markets. However, you are guaranteed a minimum of $10/hour."

The site is even more honest in describing what its like to drive for Lyft: "Sometimes it is slow and you barely make anything, but other times you can make hundreds in a night. For every slow night you drive, there will be five insanely busy nights when you make a killing."

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