I believe the standard definitions are:
A hobo is a migratory worker.
A tramp is a migratory non-worker.
A bum is a stationary non-worker.
I believe the standard definitions are:
A hobo is a migratory worker.
A tramp is a migratory non-worker.
A bum is a stationary non-worker.
I like those. So hobos and tramps are essentially nomadic.
Also -
Now do gypsies and thieves, preferably to music