This is my first post so I am hoping to get some replies to my questions...

I am British and my fiance is South African. We are currently in London and he is on a visitors visa. As it expires in December we are going back to South Africa to get married and then we are applying for an marriage/spouse visa.
As I am going back for an unspecified time I am unable to keep my current permanent job. I know that you need to specify in the application how I would support my husband but I am afraid that I may not have as much as they are wanting me to have. When we come back we have a place to live but we will both be looking for work. My sister is going to be helping us with money if need be. Would that make her the sponsor? And does she need to write a letter explaining this?
Thanks very much!