Charge what the traffic will bear, relative to what you think you're worth ... and as Uncle Dave advises, NEVER underprice yourself...
You might want to get an idea as to what the going rates are in your area... you could call some 'one man band' (I really dislike that phrase, although I'm not sure why) type entertainers, pose as a potential client, and try to get prices, or call a local booking agent, again as a potential client, and ask about prices...
If you're just trying to get back into the business, you may want to hook up with an agent yourself..... Just make sure you have the details about payment in writing before you do any gigs (jobs) ... some of these guys are notorious for paying late... I worked for one here in RI and I was sure he paid so late hoping you would forget he owed you the money ...
t.
PS ... How do you do the 'bellows shake' on a reedless accordion?!? ....
t.