Bear in mind that, most programmers do not get paid overtime, and are expected to work like horses. The reason freebies are sacred rights are because those are, in part, the unofficial payment for working in such conditions.
For what is worth I'm in Japan so YMMV but I think this generally applies anywhere: if you switch from overtime-exempt to a hourly contract and keep working the same hours, your base monthly salary + overtime pay will be (in average) the same as your current salary.
The catch is "in average". Most corps will avoid having you do overtime if they have to pay extra for it, and conversely will try to switch off-hours support work to salaried employees. So you might end up working less hours and earning less as a contractor -- and sometimes that's what you want anyway. In other cases workers manage to game the system; in some orgs I know the contractors work longer hours than most non-manager salaried employees.