Hope the Architect is registered, otherwise you will be 'cutting corners' at your own risk. eg if a building collapeses and you 'cut corners' you will be at fault, but if you used a proefessional, one has a case and you can even sue them for damages.
For the 6% it is a fee set out by CAP 525 of the Laws of Kenya which guides architects & quantity surveyors. though it all depends on the services you want to procure from him.
I would suggest you also get a Qunatity Surveyor for cost estimation, cost control, contract documentation etc
Jamaa wa mjengo