1. Since there was no will, the estate is to be distributed in terms of the Intestate Succession Act. There is a whole list of scenarios that exist, depending on which relatives is still alive. If your father was married at the time of his death, then the whole of the estate will go to his wife. If he was not married, then the house will be divided between his children in equal shares. This means that both you and your sister and if you have other siblings, them too, would inherit the house.
2. From the above it should be clear that you would not be able to get the house in your name only. Neither would your sister. Her daughter would have no claim whatsoever. The transfer of the property must go through a conveyancer. For a property of R 100,000.00 however, the cost is most definitely not R 17,000. It should be a lot less. Closer to R 8,000 - R10,000. So shop around for attorneys.
3. Your sister and her daughter can threaten all they like, but they are not going to succeed with legal action to evict you from the property. Only the owner or someone placed in control of that property by the owner or the Municipality may evict people. So, they have no legal standing to bring an application like that.
You can ask the Legal Aid Board for assistance with the disputes between you and your sister and you can ask the Master of the Court or the person designated for it in your Magistrates Court to assist you with the administration of the deceased estate. You can ask the Law Society in the province that you live for assistance in appointing a pro bono attorney to transfer the property. There is still going to be expenses, such as the deeds office fees and suchlike, but those are probably going to come to R 1,000 - R 2,500.
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