You owe this man nothing other than friendship and that can be done from a distance should you wish to keep it going. Get away before his family depend upon you even more than they already are. You are young, and should be enjoying holidays and trips with people who treat their friends with mutual courtesy and respect. Seeing him every day could soon drift into cooking his dinner, doing his laundry.....all things which are up to his family to organise if he is no longer able to do so. There are many on here who will tell you how difficult it is living with dementia (if it is that, not just being a bullying pig), and they love the person they are caring for. To be blunt: In 10 years time, if he is dead, will his family thank you/take care of you financially/compensate for the loss of your fit healthy years? I very much doubt it. Move away, visit your family in Australia, break the pattern of bullying dependency.