A few questions for you??
Is it a full or part time position?
What are they paying for vs. what will you have to pay for? (Lab fees, CE courses, professional association fees, health insurance, retirement benefits, etc)
Lastly, the comparable salaries in the area
Worst case, you ask for too much, and they counter with less, if it's a number you're happy with, fine and dandy! On the flipside if you ask for a number, and the immediately accept (maybe even with a slight grin on their faces) then you just found out that you could of asked for, and gotten more
Personally, as an employer, if I asked a potential employee that question, I'd almost expect that potential employee to ask for more than ""true market value" and then begin the negotiation from there, so I'd advise you to ask for a salary that is higher than, but not ridiculously high for the area. Or even a situation where you get a base salary and then "bonus pay" for if you're productions (ideally for your perspective) or collections (realistically from the practices perspective) are over a certain amount each month - kind of the best of both worlds for each party in that case. You get a set minimum income, and then have incentive to grow your patient base (both you and the practice owner will like that) via getting greater pay based on doing more work