You can open a joint savings account with a bank. To keep costs low just keep it as a personal account, not a business account which usually carries higher fees. Nedbank pays good interest rates on relatively low balances so may be worth considering. So does Capitec and FNB savings account.
If you want to open a business account in the future it is worth doing your homework first to see which bank has the best package and then start your savings account with them and consider moving your transactional banking to them. In this way you are both building up a track record.