I have two principal constraints: a small back yard with a large amount of bushes and plants. The advantage I have is knowing how the big railroads built there property.
I started much as MR I.K.Brunel did. I surveyed (actually just looked) at where I intended to lay track; laid a firm base in a shallow trench in the dirt which went right around my garden. Once the track was completed and electrified I ran trains. Like many real and model railroads extensions and revisions have been made over the almost five years it has been operational.
My wife deals with the horticulture and was very helpful during construction work with plants, bushes etc… As a result there are not many places where structures can be sited so apart from a wayside style station, small freight depot, tunnels and a few small lineside buildings no major building developments have taken place.
Generally speaking the 1:1 railroads built, outside the larger towns, piecemeal, providing facilities - and removing them - when required and when not. The United States is a very large Country - my models represent American railroads not European - so I am content knowing that there are long stretches of railroad where little, other than the natural landscape, exists.
I am happy with it and one thing I believe is good about large scale railroading is that there is always something to make or maintain. lol