I bought a quad in a C area, not a high crime area, just working class. We renovated the building upon purchase; new siding, new roof, new windows, new hand-rails on each unit, the works, plus a new AC on one unit. After the work was done, I was hit hard with move-outs, evictions and vacancies. Some of the tenants though that I would raise the rents to pay for all the work. Truth be told, the property was a good deal when I bought it, and I got the seller to pay for most of the work, apparently he really wanted to sell.
When we were trying to place new tenants, we were having trouble getting any interest. We advertised on multiple web-sites, had a big sign up by the high way, nothing. We even offered 1/2 month off discounts. Nothing. We then raised the rents about $40 a month, and with in a week all my vacancies were gone.
My take away was that even though it might not be the nicest part of town, people still have their pride, and if the price sounds too good to be true, they will not even look. Had I know that raising the rent was the answer, I would have tried that first. Since then, we haven't had any issues, and I have encouraged the other owners on the block (all quads on the street) to do the same thing.