Carol, I just took a quick look at the inventory (as per MLSLI) and found the following inventory in Queens/Brooklyn under $400k::
907 homes (including 130 2-3 unit properties)
Brings up lots of questions. A multi-family, single family or condo? How much property management are you prepared to undertake yourself? Preference for neighborhood types? Marginal, up and coming, established, toney?
In regards to Jackson Hgts, it's a very attractive location w/a nice supply of units at modest to moderate prices. I'm familiar w/the area and have seen it's rise since I helped start to terrific schools there. In terms of current inventory, there are 26 condo units for sale under $399,999--a couple 1 bdrms as $269k, and 119 coop units (ranging from a $119k studio to a $389k 2bdrm in the prime historic district).
Lots of great choices.
Carol, Let me know if you'd like my assistance in your search.