A USDA loan is backed by the Department of Agriculture's Rural Development office, and the first question it asks has nothing to do with your finances. It asks where the house sits. You do not need a farm or a gravel road; the program's definition of rural takes in a surprising number of suburbs, exurbs, and small cities. What you cannot do is argue with the boundary. An address is either inside an eligible area or it is not, and the official
USDA property and income eligibility tool gives a yes or no for any address you enter.
The boundaries also move. As Census data shows an area's population growing, neighborhoods get reclassified out of eligibility, so a subdivision that qualified when your coworker bought there in 2020 may not qualify today. This is why the map check belongs at the very start of a home search rather than the end. The most common USDA disappointment is entirely avoidable: a buyer falls for a house, gets preapproved on income, and then learns the property line sits a quarter mile outside the eligible zone.
One more distinction before you start. The loan modeled here is the Section 502 Guaranteed loan, issued by regular private lenders with a USDA guarantee behind it, and it accounts for the vast majority of the program's volume. A separate Direct loan, issued by USDA itself, serves very low-income buyers and can subsidize the effective rate down as low as 1%. If your income is well under the area median, ask about the Direct program before assuming the guaranteed loan is your only route.