Is the property rent ready or are you about to do a rehab? How old is the property?
There are two tests - the dust wipe and the XRF test. I would recommend the XRF test. It is more thorough of the two and its only another $100 more. The dust test will tell you if lead is present, but the XRF test will tell you exactly where lead is throughout the interior and exterior of the home.
Lead paint was banned in Baltimore in 1950, so homes newer then that will cost significantly less to remediate than those build before. (some home built prior to that might not have much lead either, but you wont know until your test) In those homes, you still will probably have lead paint in the exterior, but that is easy to fix by wrapping the windows - and replacing any original windows.
Give Lead Tech a call and they can tell you all about it:
http://leadtecservices.com
Something to consider. In Baltimore, there are no limits to the landlord's liability if they are sued for lead paint, so it's always best to go lead free if you can.