Every culture is different regarding pets in the homes. (I think in Arabia at one time it was the norm to keep horses in the house).

The risk of a disease or accident basically are very, very high for an outdoor kitty, even with full vaccination kept up to date.

The average livespan of cats:
Outdoor kitty - 7-9 years
Indoor kitty - 14-18 years
(remember this is only an average)

Neutering and vaccinations do increase the chances the cat will live a longer life, but given the dangers outside they do nothing to prevent accidents or deliberate foul play by very mean and sick people.

Even if the OP doesn't come back to read this, I wanted to post it for the benefit of others who may read this.