It takes a long time for hot water to reach my bathroom. I am considering installing either an additional hot water heater near the bathroom or a return circulation line. Which would be the most economical over time? Also, if I chose the return circulation line, is there anything specific I need to know before hiring a plumber, such as where it should be installed?

I had the same problem, installed the Watts instant hot water recirculating system and it work fine.

Your no "plumbing dummy " with a question like that.
You will have less operating costs and upkeep with a recirculating line. A water heater will pull 19 amps when its operating a circulation pump will cost pennys. They even make a recirculating system that doesn't need a return line, Comfort series hot water systems from FAMOUS PLUMBING SUPPLY or you can clicki on these for more information. You can go with a pump,
Hot Water Recirculation Systems
Or a gravity system, Gravity Hot Water Recirculating Loops
Good luck in whatever you decide. Tom

Might want to consider a D'mand system or Autocirc, you won't need two heaters. Advanced Conservation Technologies: D'MAND Hot Water Systems

Tom is right
I hope this link will help you I installed the watts recircullating pump last year and helpded

Amazon.com: Watts Premier Hot Water Recirculation Pump, Blue #500800: Home Improvement