The problems of operating in a built up area are obvious really. There is
a need to minimise visual impact and the use of long yagis at VHF is usually
not possible purely because of plot size. In my case I am restricted to a
maximum boom length of 4 metres before encroaching on the neighbour's air
space.
The prospect of persuading the local authority to give permission for a 15 metre, or even a 10 metre tower on a suburban plot, even if you have space, is likely to be limited, to say the least. The likelihood is that your support system will be an arrangement of poles and T and K brackets with mast space for only two or at most three antennas. A Ladder will probably be needed for access and maintenance and changing antennas for either experimental or contest purposes will almost certainly be more than a ten minute exercise.
There are likely to be several amateurs within close proximity who will be operating at the same time, especially during contests, so an aerial system with deep nulls is especially useful.
For HF, even a mini beam may well be impractical (supposing you can keep it up in the air in anything other than a light breeze) and the chances are your neighbours will not look on it with quite such a fond eye as yourself. You may be able to smuggle a vertical past the xyl and the locals but in a substantial number of cases some form of wire aerial will be all that is possible.
In this section I have detailed my own battles to to transfer rf to the ether and would stress that in an urban environment whatever you do is going to be seen by someone and not all the people in the locale will share your enthusiasm for the latest piece of aluminium you have hoisted into the air. It only takes one disgruntled person to contact the Local Planning Office and your life will become a misery. Take note of the local planning dictats, bend them, even break them but don't upset the locals. Always be considerate, friendly and helpful - your radio fate is in there hands.