Hi,
Largely agree with the previous post.
Nairobi is safe, as long as you take precautions: Don't drive around at night too much, certainly don't walk on the streets after dark, or through the parks, alone. Keep out of the poorer areas. Don't act as if you are lost. Don't walk around talking on your mobile, or pugged into an mp3.
As with many large cities, you just need to be aware of what is going on around you.
Get a Safaricom sim card and then register to use 'M-Pesa'. This is a mobile money service, where you have a virtual account on your phone. Many goods and services can be paid for, using this including shopping. It means that you do not have to carry cash. It is secure, so if your phone is lost or stolen nobody else would have access to your money (unless you have the passwords stored on the phone itself).
Employees: I think it unlikely that you would be able to hire an Indian domestic help. Kenyan Indians don't employ other Indians, on the whole. I understand that the government are on the point of increasing workers rights, to Ksh 8000 per month minimum wage, plus housing allowance and two days off a week, annual leave etc. If you want a driver, check them out carefully. A driving licence does not indicate competency to drive. In fact make sure any employees check out properly - they are going to have access to many aspects of your life. If possible, get your workers through personal recommendation.
Accommodation: You mention a villa. These are available, but tend to cost considerably more than apartments. Recent years has seen a construction boom, with many individual properties being replaced by apartment blocks. It depends on what you want and your rental budget. For example; Westlands has a large Indian community. For the type of properties available, you can check out the websites below. There are others:
hassconsult.co.ke/hass/index.php
villacarekenya.com/
knightfrank.com/property-to-let/kenya/nairobi
nairobirealestates.com/public/rentals.do
I am not the best person to advise on prices, as I own my house!
Vehicles: A imported saloon car is fine for the city. If you want to travel upcountry only occasionally, then you can rent a 4x4. If you want to get out of Nairobi regularly, buy a 4x4. Nairobi is full of dealers, selling imported vehicles, prices generally start at around Ksh 500 000 - 600 000, for a small saloon.
The shopping malls have notice boards where vehicles are posted for sale. Buying new is very expensive, but the advantage of buying a local market vehicle (new or used) vs an import is that it is 'africanised' to cope better with the local conditions, and over time, should be more durable.
Domestic Travel: We drive about quite a lot, with no problems at all. The biggest risk of being in Kenya is actually being injured/killed on the roads, rather than being mugged/attacked, especially on public transport. Some of the northern places can be unsafe to drive to, but flying is an option.
Food: Much cheaper to cook at home. Although food prices are increasing, you can keep costs down by shopping at markets, rather than supermarkets. We spend around Ksh 8000 - 10 000 per week on the family and animals.
Hope this helps.