Joining the SA YWP
To be a member of the SA YWP, people can be either WISA or IWA members - they don't have to join both.
The WISA membership information is on the internet at http://www.wisa.org.za/membership/membersh.htm
and you can also download the application form here. Since WISA members have to be proposed by a current member, feel free to download and complete the form, then if you do not personally know a WISA member, email the completed form to one of the contact people above to act as your proposer. Student membership of WISA is free (only a R50 joining fee applies), while most other grades of annual membership are R440 (plus R50 joining fee for new members) for 2010.
The IWA membership info is online at IWA's membership page. You can join IWA instantly online at the individual / student form webpage and the fees are all listed by the IWA, but note that IWA has a two-tier fee structure. Members from Low Income Countries pay a discounted rate (see the PDF list- most African countries including Namibia, South Africa, Zimbabwe, Zambia, Mozambique, Malawi and Botswana qualify for 40% discounted rates, so the individual membership fees are only US$51, approx. ZAR360 at the time of writing, and for students US$31, or approx. ZAR220).