However, it will may also depend on your status: ….full-time/part-time…you level of education (degrees…BA, MA, PhD–full PhD or about to be conferred)…number of units after any one of those degrees….tenured / non-tenured…and sometimes the part of the college/university you are in (dept, program, etc.) and the terms of your contract (which may limit the number of hours of teaching vs research)…and at some schools, the influence of the union or the contracts.

In some cases, your contractual load is based on a salary schedule…and overload is calculated on an hourly wage scale which is linked to your salary (which may not be directly proportional…often a scaled % so the hourly wage is a fraction of what it might be if you calculated your contract teaching load / salary to an hourly rate).

Most schools / unions may also have agreements in place that part-timers cannot teach over a certain “load” or the college must hire them as full-time and provide benefits….

Most schools have formal contracts for all teaching assignments…so it isn’t simply asking you to teach as a verbal contract…it is a formal written document that clearly specifies the number of hours and the pay rate….and certainly if they initially approach you verbally to check on your availability and willingness…you should ASK for the terms (e.g. hours and pay rate).

So, again, the last part of your question (and sub questions) can be most definitively answered the the Human Resources/Personnel folks. The salary schedule should be available and should lay out all of this information. If you are in a public college/university…this info is a matter of public record and available upon request. And it can change whenever the college/university negotiates the salary changes (most often on an annual basis or whatever the specified contract period).

However the overload pay is set, it is unlikely to be negotiable, so whatever it is relative to your other teaching, it will be what it will be….so you simply decide if it is worth the money to do the extra work, if you need the additional teaching “credit” to build your resume (as it might involve classes you may or may not have taught before)….or if you can make more doing other work elsewhere.

To get info for other schools, contact them and ask for their salary schedules. Or for something more generic just for an rough idea…try something like www.salary.com and type in college professor…and different city/state names to get an idea of the geographic regional pay scale differences AND benefit packages….but these are often statistical “averages” so individual school data can still vary considerably.

Hope this helps guide you to your goal. Best wishes!