As an employer we usually ask what salary the applicant is expecting, we usually do this on the application form. If their expectations are too high or out of line with what we are willing to pay then we would reject them. I think we've only negotiated on salary once in all our years. That person negotiated a higher salary but they only lasted a few months as they couldn't live up to the salary they asked for. Just a warning!
I dont think there's any harm in asking about advancement within the company, with associated pay rises. This approach might look better to the employer than asking for a high salary to start with. Remember, if youre going through an employment agency the employer is already paying a large percentage of your first year's salary to the agency.
I think youve answered it yourself though - if they are keen to employ you then they'll offer a bit more.