Apples are reliable and heavy croppers (usually), and are a fruit that everyone likes. Unfortunately for people in subtropical areas, they usually require more winter cold than subtropical areas provides. Most importantly, they start bearing very quickly. The range of flavors is the most extensive and complex of any fruit, encompassing perfumed, anise, honeyed, spicy, and with a wide range and combination of sugar levels and acids. In addition, the flesh can be so soft it is almost 'melting', or it can be so dense it is almost 'hard'. And the texture of the flesh can be coarse, or very fine.

Espaliered trees should be on a semi dwarfing rootstock such as MM106 or Northern Spy. Espaliering apples grafted onto a very dwarfing rootstock such as MM9 is only a good idea for very vigorous varieties. For the apple of average vigor (most apples, in other words), the dwarfing effect of espaliering plus the dwarfing effect of a MM9 type rootstock is just too weakening for good production.

Small free standing 'bushes' can be created by buying a tree grafted to an ultra dwarfing rootstocks such as MM9. These mini trees do needing staking. These are a good option, as they require relatively little attention.

Dwarf trees, either espaliered against a wall or fence, or as small bushes, are the only game in town for the small garden. 

The two major problems are codling moth and bird damage. Moth can be confused by placing pheromone lures around, and birds can be netted out of the tree, or a variety of cunning and reasonably priced commercial bird scare devices can be tried. Some apples are subject to some quite damaging fungus diseases unless they are sprayed; however, there are disease resistant varieties, and most varieties will get by with indifferent attention to copper sprays. Most of us move house so frequently that by the time a tree is perhaps badly affected, we will have moved anyway. Conversely, remove badly diseased trees you may find in a property you move to and start with healthy new stock-but don't plant them in the same place as the old trees were removed from.
 
Disease resistant apples for home gardens are discussed at this page on the Cornell University site. The cultivars are American, but most are available in the Western world.
http://www.fvs.cornell.edu/Faculty/php/MarvinPritts/Ornamentals/page3.htm
 
The kind of apple or apples should be decided by the purpose you have in mind-cooking or fresh eating-and what you like. The range of low chill apples for sub tropical areas is relatively limited, however. Some like complex apples with high acid and high sugars, such as 'Cox's Orange', others like perfumed sweet apples with low acid, such as 'Gala'. In the flush of the season, apples are relatively cheap, so a good strategy is to grow an apple that is simply not available, and that has superb eating qualities. Paradoxically, even common commercial varieties can reveal extra sweetness and depth of flavor when they are allowed to hang on the tree longer than would be commercially feasible, and when their soil is amended with lots of organic material and flavor promoting materials such as seaweed and fish manure leaf sprays.

Virtually any soil will grow apples, but light or sandy soils need to be mulched and watered in summer, especially if the weak-rooted MM9 rootstock is being used. The trees need to be kept healthy with good nutrition and summer watering.-an apple tree is said to need at least 20 leaves to mature one fruit. It is advisable to keep pruning to a minimum, but any pruning that needs doing should be done in summer, even if you have to sacrifice a few fruit. Winter pruned trees are very likely to get a fairly serious disease called 'silverleaf' unless each cut is treated with a top quality wound sealing paste, or unless the tree had been vaccinated against the disease early in it's life.