What happens when a farm is held by several heirs and one of them wishes to sell his share? 

He must offer his part first to an heir with the right to first refusal. In the first two years after the Inheritance or Probate Order is given, each heir has the right of first refusal regarding another's share. After that period is up only an heir who registered his preferential right within the first two years will retain it.

Can heirs make an agreement between them whereby a farm they inherit will be divided differently than the way in which the law provides? 

Yes! The heirs are entitled to make an agreement about how a farm they inherit is to be divided, and can override the provisions on this set in the Inheritance Law of 1965.

Will the heir who can offer to pay the most have the best chance of buying the farm which is inherited between several heirs? 

No! The farm is designed to be transferred to the heir who is willing and able to

keep it on, and not the one who can pay the most to buy out the others.

No! The heir is not limited to the type of agricultural activity that exists, and can do something different, providing the property is kept on as a working farm.

What happens if the surviving spouse, who has rights in the property due to their long marriage, does not want to keep the farm on as a going concern? 

Where the surviving spouse's rights to the farm derive from the presumption of partnership in marital property, applying to couples who married before January 1st 1974, the obligation to keep on with agricultural activity does not apply. The surviving spouse is free to occupy half of the farm, and do nothing with it.

Yes. Firstly, the surviving spouse , who has 50 % rights in the farm under the 1973 Spouses' Property Relations' Act , can only continue to possess half of the farm if he/she is willing and able to keep it on as a farm, and if this is so, will have to compensate the other heirs for the half in which he/she has no rights .

Can testator give instructions regarding a farm he owns which will effectively result in its end as a working farm? 

Yes, a testator is free to give instructions regarding how the farm is to be divided after his death, even if this results in its liquidation.