Question for Real Estate agents/property developers....

[ian]

But the developer has to be able to sell them all within a reasonable time frame.
If he can't then a staged development might be a better option.

and once the original purchase option expises, and in a static or falling market, the developer might be the only buyer for abitfishy's inlaws

ian

[Honorary Bloke]

And if and if and if . . . .

Pretty typical give and take. It can get fairly convoluted quickly. That is why, at least here in the States, buyers and sellers retain separate agents to negotiate these deals.

Lots of good advice here, but almost too much for a bloke that's just trying to "help out." Fishy, think about employing an agent on their behalf--he/she will likely pay for him/herself in improved terms and pricing and take the worry off your shoulders.

[Disclaimer: this assumes that, as here, buyer's agents and seller's agents are licensed and have a legal, fiduciary duty toward their clients. If that is not the case, I wish you well.]