I'm in the west of the U.S. but I work with a company that mostly does midwest and east coast. I could have some jobs closer to where I'm located but this company has treated me well so I've stuck with them for now.
As far as making your own hours it depends on the gig. Typically if a hospital has locums needs they want to credential as few docs as they can in order to fulfill them. Sometimes this means they want people to be able to cover 1 or 2 weeks a month firm. If you can't fulfill that then you obviously don't work there. Also some jobs might want you to read EEGs and if you're not comfortable then same thing. Both you and the hospital have ~30 days to cancel on each other if it's a bad match. I've been canceled once due to the hospital canceling locums completely. I won't work again with a place that cancels on me (this particular place tried), and I don't cancel on hospitals once I've made a schedule. This allows me to have relatively stable jobs (1 week/mo for 6 mo, for example).
Typically once you've accepted a job and you're credentialed your locums agent will give you a list of open dates. It's usually first come first served regarding dates among the locums that work there. If the company likes you you might get first dibs on dates or first refusal on a job, particularly if you're a good fit for the place based on your work history.
This year I'm working ~21 weeks between a cushy per-diem job and locums. Granted the schedule isn't always sweet. I worked 5 weeks in a row at one point and sometimes I'm traveling 5-6 hours across time zones every other week for a job. That being said, from the 2nd week of Aug to the end of the year I work 4 more weeks clustered in October/November and then I'm done. Off for Thanksgiving, Christmas, and New Year's.
Typical pay depending on call, hours worked, and volume at most inpatient gigs is ~2500-3000/day, with some days making 3200-3500, and 1.5X multiplier for federal holidays.
Hope that helps.