Personal effects and furniture

I don't believe that there are any duty free allowances, unless you are a returning resident, or coming to Kenya with a valid work permit. 

As for shipping a car.........it must be under 8 years old and right hand drive.

For shipping, you need a company with a clearing agent in Mombasa, or appoint a clearing agent before your container arrives.  Duty can be considerable and is based on cost + insurance + freight, so not just the value of the goods.  With other taxes and charges it can amount to around 75% of the value of the shipment.

Allegedly, the port has a considerable number of abandoned containers of household goods from people who have underestimated the cost of clearing.

As for the visa:  there is no 'retirement visa' as such.  If you have a income from pension/investment of $24,000, or more, you would apply for a 'Class K' permit.  This is normally renewed on a two yearly cycle at a cost of Ksh 200,000 plus Ksh 10,000 admin fee.  You can apply for Permanent residence after 7 years (less if you are married to a Kenyan citizen).

The Class K permit can be a bit slow to process.  You will need to extend your initial 90 day Single Entry Visa by a further 3 months.  In my case, the Class K wasn't approved before my Single Entry Visa had expired, forcing me to travel out of Kenya, for a few days, then return. 

To remain in Kenya legally, you must have a valid visa, or permit, unlike, say the UK which allows a person to remain in the country while an application is being considered, even when the original visa has expired.

Hi.
I dont know if there is a different between retirement or just moving like i did one month ago from Sweden. All my calls to immi and ambassy said to me that the personal belongings should not be tax or duty on.
But when the boxes arrived to Nairobi the custom wanted 24000ksh before they released them. So you never know how it will go.