You might buy a pair of walking sandals from an outdoor shop. They are not as heavy as shoes or boots and you are less likely to develop blisters. Start walking in them until your fitness is kicking in. They won't be wasted as I use sandals on the Camino whenever I can and only use boots in rain or over difficult terrain.
As you get fitter buy and break in either walking shoes or boots. Check the FAQ's on this issue. You will find that there is disagreement about what is best; walking the Camino is much an art as a science.
You need to walk with a day pack so that water and food are both on your back and to hand duriing the journey. As you get fitter slowly add more weight.
It is better to walk every day and build up slowly than doing long, mad walks over the weekend.
Coming from SA will be expensive so you don't want to have to give up because you have not got yourself to an adequate standard of fitness.
Don't worry if you are not walking the km/mileage that the Camino requires by the time you start the journey; few of us have the time during the day to achieve that. When you are on the Camino you will build up the stamina. You will also find that you will continue to lose weight so bring a belt for your trousers; we all need one.
The important thing to stress Theresa is that many of us are not super fit, a number of us have health issues, but we still can walk the Camino because we did some preparation to make sure we did it.
If you find yourself struggling don't give up. If you need motivation buy a metal scallop shell from
http://www.pilgrimsupplies.org/ (I am a friend of the website owner but receive nothing from him!), put it on during the practice walks and swear, next year I
will wear this on the Camino Francés and keep persevering.
If you need more help that is why we lurk here.