Well, ten points for being very thorough in what you're seeking, but it sounds like you're particular enough you really should be here in person to check out what's available. I personally don't think it's practical for you to expect this sort of place to be ready-to-go upon your arrival. As per the typical advice of many on the forums, I'd recommend you arrange temporary accommodation for the first couple of weeks of your time here, which gives you time to look at places in person and get a feel for various areas.

Some other brief feedback:
* A separate house/villa will generally cost more than a flat/sharing a property (eg having someone upstairs, or being upstairs). As you go further out of the main areas, the rents do drop. But I'm not sure if they drop as far as $500 for a house that has everything the way a barang would like it. Maybe they do. I'd expect that such houses would have inflated rents these days, in areas with easy access to the ECCC.
* Gardens and yards are rare in Phnom Penh. Generally only found with villas, and not all of them.
* Yes you are correct, the ECCC is outside the "main" city area. If you or your husband are on UN staff you should be aware that they usually have requirements and restrictions on what is allowable housing, including which areas you can live in - contact your HR or security area if that applies to you.
* There's a wide variety of options now for internet in Phnom Penh, and you can generally set up within 48 hours on working days. Might take a little longer if you're not in central Phnom Penh, and you may find you have fewer options too. Googling easily shows you the range of options. You can also start by searching these forums for "internet".
* "Reasonably quiet" is particularly relative in Phnom Penh. Especially if you're living in an area not dominated by expats (I should add, even if you are), you'll have weddings, funerals, workshops, merchants, markets, traffic and other local colour to keep you on your toes in most suburbs. You should definitely check out the area at night time to make sure you're not renting within screeching distance of the nearest karaoke restaurant.
* "Safe neighbourhood" can also be relative. Another reason to turn up and check things out in person is to make sure that "safe" matches your expectations and you feel safe in the area in question. And safety will also depend on your habits and behaviour: shows of wealth, friendliness with neighbours in surrounding area, taking reasonable precautions, etc.
* I have no idea but I would guess that any places like those you're describing, at that price, if they were around would already be filled by interns or others from the ECCC by now.

Finally I'd suggest you get in touch with this guy: Art the Homefinder (see http://www.expat-advisory.com/forums/real-estate-agent-recommendations-p...). Give him a heads-up about what you want, and arrange to meet with him when you arrive to visit a variety of places that he thinks suit your requirements. With some notice he should be able to prepare a list of places for you to look at. He's dealt with quite a number of foreigners so he's well placed to understand what you're talking about, and I'd say this could be your most likely way to find what you're looking for if it's out there.

BC

Dear BC,

Thank you very much for your detailed reply. I've been checking this forum fairly assiduously for months now, and the reason my request is so detailed is that I read your advice about providing information so that people can help me better. Here's one person who took your advice!

Sorry if I came across as a bit of a madam, but the husband will work from home and he needs his peace and quiet - and his bathtub! I'll be the one working at the ECCC.

About noise levels. I'm from West Africa, so funerals blocking the street, welding and carpentry workshops next door, barking dogs, time-keeping cockerels, vociferous religious events, discordant and enthusiastic singing of all kinds, animated and fairly physical family discussions, and the particularly unamusing case of landlords wanting an advance on the rent to pay for a trip up-country all strike a chord.

What I cannot ignore I can bring myself to enjoy. Not the husband. He prefers watches to cockerels.

I saw something here a few days ago about a house/flat in Russey Keo (spelling?) and I'm looking at that. I intend to get a friend to nip over there and look at the property. There appears to be a housing estate there within the limits of my purse. Does anyone know anything about a housing estate over there? Is it a good place to live? I don't mind living out of the town centre as long as I have a jalopy to go grocery shopping and I can get to work easily.

Re safety levels, I expect to be at some risk outside the home (who isn't anywhere in the world?), but I'd like to be reasonably safe at home, meaning a low level of break-ins and not being terrified each time you drive home in the dark that someone is waiting for you to get out of the car so they can rob you - experienced quite enough of that in my home country. From what I've read of PP, people will leave you alone unless you tempt them by dangling a handbag in their face.

Thanks again.

RE

here is another world famous BC post on tips for finding accommodation

how to look for accommodation by BC