I had a friend who waited until her wife died before transititoning. Her name was Stephanie Bishop - and when she began transitioning, she was 79 years old.
She lost her friends and family on coming out, even her children and grand children were too conservative and short sighted to accept this - I know she cried many bitter tears over how nasty they were to her. But she was financially independent, moved to another city (where I met her) and got on with her life. She was delighted by the tendency people had of underesimating her age by 20 years or more and endured many jibes about her "toy-boy" suitors who in many cases were twenty years younger than her. I doubt she was ever lonely again, as most people her age often are.
She died when she was 83, three years after her final operation - but she had three good years of life, an active social life, new friends, new love - and even the title of "best dressed lady on the block" where she lived. I know very few 83 year olds who can send and read an sms - or an email - or have more dates in a week than somebody half their age - and yet she did all these things! Yes, she died after three years, but she died happy - and fulfilled in the form she wanted to be in. And she was loved. She was a good friend.
Starting early is best, but not always possible. Many of us have regrets for not starting earlier, even me. We go on day after day, living lives that are not our own - to go on pleasing others by disregarding out own needs - and with each day making ourselves more unhappy. But we are what we are - and that never goes away. So don't leave it too late. Be happy.
While there's life, there's hope.