Selling and a living will

Hi there
This is a bit complicated but my sister wants to sell a house in Ireland, she lived in South Africa. The house is register under her name through my Grandfathers will, but my Father has a say in weather the house can be sold or not and is entitled to the rental income of the house. My sister only has full control when he dies.
They have agreeded to sell the house so my sister can buy out hers in South Africa but they need to agree on what percentage they will each get.
My father is 70 years old a control freak and one mean bastard, so my fear is that he will try to screw her for as much as he can. He knows my sister desperately needs the money and will try to use this to get as big a share as he can.

Is there any way of working out what a fair divide would be. Obviously if say he were to live till 85ish thats a loss of 15 years rental income but he could also invest his share of any sale.
Any suggestions would be much appricated, it a tough one I think

There are actuarial formulas available for figuring out what a life interest in a house is worth for a male aged X. Perhaps have a look at this and make an offer based on that?

I'm not sure that she can sell it without his full agreement. He has agreed but now its down to percentages. He can (until there is something in writing) or something enforceable delay, prevaricate, etc.,etc. Ideally, they should agree the percentages and he should give her an irrevocable Power of Attorney to sell and she should sell p.d.q.

I reckon from what you say that he may cause trouble. Mind you, it might equally suit him to get a lump of money now. I think Vanilla's idea is good - get a figure out there and then see just how much he actually wants and whether he is serious about selling or just winding her up.

mf