The starter relay is clicking - it's probably ok.
New battery is probably a good idea - if it's the original in a 2003 it is probably toast.
Beyond that, honestly, it's kind of hard to help from "afar" as it were.
If he was afraid of doing anything to the bike, the possibilities of problems are great. Not insurmountable, but more than anyone can answer here with the info provided so far.
Does he have any service records? It should have had a service at 500 miles.
Start with the new battery, some new fuel, (drain the bowls on the carbs too), and make sure nothing is living in the intake or the exhaust.
After you drain the bowls - a spray paint can cap makes a good receptacle - open the petcock with the new fuel in the tank and check each bowl again to make sure the fuel is flowing that far.
The price is right for investing a bit to have an 03 Bonneville America.
Good luck.
