Going solo in Nairobi?

I have been offered a job in Westlands Nairobi and will be moving initially without my partner within the next month, so I have a few questions with regards to this:

1) With an accommodation budget of around 50k a month I'm gathering that I will only get a house-share for this? I don't want to live super central (e.g. be right on a main road etc.), but somewhere close to work in a relatively peaceful/green setting. 

2) What are my best options with regards to a gym around the Westlands area? I like to do classes as well as use the gym.

3) Is having a car in Nairobi essential, especially given that I will be a lone female for a while? I've never been without a car and am worried about the astronomic prices of buying one! Also about the limitations of not having one with regards to weekend trips etc. I currently live in Botswana and have been considering importation of a car but can not seem to find anywhere that clarifies whether I would be entitled to a duty free importation... I would be working for a conservation NGO who will be sorting my work permit if this makes a difference to entitlements. 

Appreciate your feedback!!