What if my drainfield needs to be a long way from my house?

That is common on lots where the only suitable soil is at the back of the property. It is usually solvable: the tank stays near the house, and a pump tank sends effluent through a small pressure line to the drainfield, which can cover a long distance and go uphill within the pump’s design limits. The trade-offs are cost (pump, alarm, electrical, longer trench), a maintenance obligation, and the need for the pipe route itself to respect setbacks and stay off future driveways. Some owners also need an easement if the best soil is on a neighboring parcel. Plan the route on the site plan before you commit to the house location.