When playing Start From Scratch, you only have $500,000 to begin. With even the cheapest field on the map running at $107, 496, it's obviously important to pick a good field to start with.
First we have to determine equipment costs. After testing, I've determined that harvesting 1 field will not pay the lease cost on equipment, so we will be buying our equipment instead of leasing.
Italicized items are for grain harvest, underlined for corn/sunflower and bold are for baling. Normal text indicates it is used for either application.
I picked the Fortschritt HW 80 over the Strautman SEK 802, even though it's slightly more expensive, because it has more than twice the carrying capacity as the base model SEK 802. To get the same equivalent capacity in the SEK 802 would cost $11,000 (halfway between the 8k and 12k capacities)
In case you're wondering why potatoes, beets and cotton are not on the list, it's because the starting equipment for those require more than $500,000.
So, after buying your equipment, you will have either $300,600 or $296,600 remaining. This eliminates nearly half of the fields as options. Of the remaining, several have been planted with potatoes, beets, cotton or grass.
Out of 33 fields, only 14 (2,5,11,15,17,18,21,25,26,27,28,31,32,33) are actually available options for your first field.

• Field 17 is the largest with 7.4 acres. It may seem like a good deal, at only $261,840 or $35,383/acre. First harvest is Soybean at an average $20,579. However, being unable to afford baling equipment, your best 2nd harvest would be Canola for $20,690.
  
• Field 11 is the second largest field, with 5.18 acres at $192,648. $37,190 per acre. First harvest would be Wheat with an average $24,294. 2nd harvest would run wheat again for another $24,294. This is the best deal out of all the options.
  
• Field 18 is the third option. 4.89 Acres for $180,192, $36,849 per acre. First harvest of Corn would net $13,647. Best 2nd harvest would be Sunflower for average $13,740.
  
• The final option is buying Fields Fields 26 and 28, 4.31 combined Acres for a total field cost of $233,016. $59,377/Acre. 1st harvest of Sunflower and Corn would bring in $12,083, while the best 2nd harvest would be Sunflower with an average $12,111.

I referenced Undying29's Guides Field Sizes and Cost and Crops Yields and Prices for field sizes and costs as well as harvest incomes.