Guess that depends on how badly they need a bolt welded on something.
Even if they bring it to you, $35 is not really that bad. You have the machine, right consumables and overhead. You know the amps, have to prep it, etc.
If you think about it.
$20 would sound cheap, but my son does little things like that all the time if they come up and he is in the middle of welding something else.
I think you really have to play it by ear to get started. Like anything else.
Also, we have 5 trailers to do this weekend from a repeat customer. Treat them right and they will bring you more work too.