A high unemployment rate means work permits are required. These can be difficult to obtain unless you have specialized skills that are lacking in the workforce. You are best off being appointed abroad, as local employment opportunities are low-paying and few.
There is a large number of international expatriates who work for non-profit agencies such as the U.N and other affiliated agencies. Their pay is very high in relation to local living standards, and as a result their employees can afford to live in luxury.
There are numerous opportunities for volunteering in Kenya, whatever skills you have. Websites such as Idealist carry details of many of these placements, which could be centered on education, conservation, community development, or a number of similar areas. Kenya's English-speaking history and relative stability despite recent events following the disputed 2007 elections make it extremely well suited for this kind of work. In most cases, volunteering can be undertaken with a standard tourist visa, although it is worth checking with your host organization before travelling as the authorities may not always take this view.
If you have specialised skills, there are a number of more focused volunteering programs available. These range from opportunities for medical and engineering placements for example, with MSF or VSO, to short sabbaticals for people with generic business experience, spent mentoring local businesses, with Skills Venture.