It sounds to me like you are looking for free money (equity) until u gain from the upside.
This is a challenging task, but not impossible. Best way is probably to look for one or two investors who are close to the family and have lots of money. Basically, you would have to negotiate a certain % share of the profits to keep for yourself and father but given the idea and land are yours, you can make a good case to keep a reasonable portion.
Or you could choose to borrow from these individuals and negotiate a favourable interest rate and repayment structure. If they seek security, they could take a charge over the land but if you knew them well, you might be able to negotiate more flexible terms.
best of luck