A couple of questions to think about, but don't need to answer here...
1. How old are you?
2. When you say 'medical staffing agency' who will you be dealing with? Hospitals? Recruiting agencies? Front office staff? Nurses? Doctors?
3. What will you be doing?
The reason I ask #1 is that it might come across as presumtuos if you put 'President' or 'Owner' - my experience in the medical field is that people can be put off in some instances of individuals 'grandstanding' (not that i am suggesting you are !) You may want to go with 'Founder/Co-Founder' but I don't think that is great - i would suggest 'Partner' and a more descriptive follow on (see below)
i asked #2 for a similar reason, but more so because if you are essentially a 'job placement' agency the job title must fit
In this case maybe 'Senior (or Chief or Lead or some similar term) Placement Officer' or 'Recruit' in there somewhere
And #3 because if you are responsible for marketing then 'Marketing' should be i your job title (or whatever the responsibility you have is
So lets now link the ideas together
Partner, Lead Placement Officer
Founder, Chief Placement Officer
Co-Founder, Director Marketing & Sales
Partner, Head of Marketing & Sales
President and Chief Marketing Officer (now that sound important!)
Managing Director, Marketing & Sales
Managing Director, Recruitment and Placement
you get my drift.
And good luck!