It varies significantly from one department to another. As an example, for an assistant professor in engineering, the starting annual salary is $80,000 to $95,000 on a nine month contract. You can get summer salary through external funding. The maximum summer salary you can give yourself is 1/3 of your annual salary. You can also supplement your academic year salary to 20 % if you get industry projects. Government agencies like NSF/DOE/DOD do not like more than 2 months summer salary. The lecturer salary range is much wider, it varies from $40,000 to $80,000 depending on the department and school.