We have eight espaliered fruit trees on the fenceline of our relatively small property. Espaliering the trees was a decision we made when we first started planning our edible garden.
SH is a lawn man and he didn't want deciduous trees blocking his mowing lines and dropping leaves everywhere. The espaliers still drop leaves but they provide a wonderful picture along our fences and don't take up any space in the lawn area.
We started with two apples along out driveway fence, two pears further around the lawn and then an apple in the corner of our vegie patch. Since then we have added another apple and pear behind the vegie garden and a Nashi pear on the fence just outside our front door, from which we harvested 3 pears in our first year!
Even after just a couple of years we have had awesome harvests and have frozen cooking apples and bottled pears for the past few years from our little espalier orchard.
The photo is of a Packham Triumph pear we planted only 18 months ago. We're going a bit different with this one and hoping to train it into diamond shapes. The blossom is gorgeous and we're really happy with its progress.
If you are limited for space I would highly recommend espalier as a way of growing fruit. There is lot's of info on how to do it online and it's definitely not as scary or as complicated as it looks.