Its a terrible time to be buying investment property in the inflated big city markets. I guess you will have a great apprecitation play but I'm thinking there will be a correction coming in the short term future. I would never be interested in waiting 30 years to get my initial cash investment back on a property like the DC example. My current goal is to get $250 cash flow a door in areas that I can self manage. I want to have as little money in the deal and refinance the private money out after a year or so.. I like to have my properties in areas I know and understand.
If you have similar goals I think Hagerstown makes sense. North End is great, Robinwood area and Dual Hwy, South End are fine as well. they are all C+ to A areas. Some of these areas are outside the city. Downtown and the West End can attract tenants that can be difficult but what cash flow market doesn't have pockets and areas that are harder to manage than others.
Sounds like people are having issues with selecting good tenants. As with any areas tenant selection is Job # 1, I'll turn them away until I find the right fit. I tell them keep communication open at all time and pay the rent. In turn I will be responsive to your needs. I have tenants that have stayed with me and moved into other properties based on this relationship. I own multiple properties in Martinsburg WV which is similar to Hagerstown. I also own in Md.