Apple trees on M27 are perfect for a small lot, or for someone who doesn't wish to climb a ladder for pruning and thinning. Renters like these trees because they are happy in a large (25-35 gallon) pot with the proper soil mix, and can be taken with you when you get your farm!
Unlike "columnar" apples, any apple cultivar may be grafted to M27, creating beautiful little trees. Trees will bear 25-50 lbs of full-size fruit when mature. Adequate sunlight is important for any fruit tree. Trees will produce more, higher quality fruit if they receive at least 8 hours of direct sun per day.
M27 apple trees require support, or will simply fall over with the weight of the apples. On our farm, we put posts in the ground (7 feet tall after installation, 20 feet apart), run a cable through the top of the posts, and tie the trees to the cable. With trees spaced 3-4 feet apart, 2 posts and 20 feet of sunny yard can support 5 or 6 trees.
M27 rootstocks do NOT like to dry out. Hand watering works. Or, if you are cabling them as described above, it isn't difficult to run a second cable from the support posts about 2 feet off the ground (under the tree foliage), attach some plastic irrigation tubing to the cable, punch in sprinkler emitters, and equip with a watering timer.
Most apple trees, including trees on the M27 rootstock, require a compatible pollinator to set fruit. I can help you here. Trees on M27 are very precocious, most bearing by their 3rd year. You don't want them to bear too early, though - remove all but a couple apples until their 4th or 5th year, then gradually let them bear more fruit.
M27 trees require very little pruning, and are much easier to care for in that respect than espalier. The apple cultivars I've selected for grafting onto the M27 rootstock are typically quite disease resistant. Trees will require planting, support, regular watering in the growing season, a little fertilizer (ask), very little pruning, thinning, and picking. If you are in an area where apple maggot and/or colding moth are endemic, your hurdle is a little higher, but successful crops are still achievable. I'll go into more detail on your options in future articles, or ask your county extension agent.