Hey there, I used to sell in Brooklyn for several years - I also currently live there and I was born and raised in Manhattan. I did a search on Trulia and found the listing I linked below. It is in a good area, i do not know how close the train is, but it should be near the W or N, the address is not disclosed.
Either way, NYC has a ton of safe neighborhoods, and a ton of properties under $500K, Staten Island, Brooklyn, Queens have these odd reputations that really crack me up. Especially since I was born and raised on the Upper East Side (for 23 years) - I believed them too. But after being in Brooklyn for the last 7 and really, intimately knowing the whole borough, I could not be happier. The food is great (way cheaper), the culture is still here, it is very safe, a ton of families and activities, Manhattan is 45 minutes by train and less than 30 by car. So, you really need to get out here and look around - you may be surprised how great and safe these boroughs are.
Check out Park Slope, Bay ridge, Bensonhurst, Gravesend, Dyker Heights, Fort Hamilton, Carroll Gardens, Boerum Hill, Ft. greene, Clinton hill, Bed-Stuy, Williamsburg, etc... that's a start.