The process of obtaining fruit from a papaya tree is a relatively long and difficult process if you live in a temperate climate. Due to the papaya's growth patterns and requirements it is almost impossible to grow in temperate climates. This is because papayas typically flower after two years of growth, yet temperate climates get annual freezing temperatures which are lethal for papayas. It is possible to provide cover from light freezes for those in zones 8+ but there is no guarantee of survival. Alternatively you may grow papayas in greenhouses which can provide protection from the winter chill in even lower zones. Heating elements may also be used to grow tropical fruits in just about any freezing climate.
Unless you live in a tropical climate, growing a papaya tree is one major feat, but even more challenging may be harvesting fruit. To set fruit, the papaya must have a sturdy foundation and vigorous growth. I grew my papayas in a raised soil bed allowing for adequate root space. Additionally papayas require a lot of sunshine, water, humidity and nutrients to produce fruit readily. The papayas in my greenhouse went from seed to fruit in about two years, but due to imperfect growth conditions and the size restriction on my greenhouse they yielded small fruits. Papayas typically grow to be over 20 feet tall, but in a backyard greenhouse this is impossible.