I would think that the usual rules prevail - i.e. Min Height Rule - not below 500 ft unless landing or taking off. However, for just how long you can be considered as "landing" or "taking off" is another matter. Prior to the eventual final approach a helicopter should be flown in such a manner as to enable it to alight safely with no harm to third parties.
Not knowing the actual congested area you are referring to I can't comment on the suitability of the flight paths in or out.
Another point to consider is the longer term exposure to persons living under the flight path into the confined landing site. If single-engine helis are frequent visitors to this site, the authorities might be keen to review the situation.