Grew up in a farming area so here are some thoughts from that time.

How far from the main highway are you?
Would you serve breakfast & lunch or lunch & tea?
How far do you need to go for petrol, will you be allowed to have petrol bowsers for yourself?
How will you refill the gas, do it yourself or delivery?
Supplies for the shop, how far to go, any deliveries?
How far are Dr's, dentists, chemists, police etc?
What is the secondary school like and how would you get there?

Depending on the seasons you will be busier at certain times, eg. quiet at harvest time.
Is it dairy, beef or crops as this will make a difference of times you open.

Not trying to put a dampener on your idea by any means. Maybe go visit an area that is like the one you are thinking of and see/ask what is viable.