Firstly, I have to state that it is possible to secure an airline job in your mid forties. However, to do it from zero flying experience is expecting rather a lot, and I think I'm fairly safe in saying not many will succeed in getting what they want. But it can be done, as previous contributors to Wannabes will no doubt confirm.
There have been some good posts in this thread, and all I can do is echo the point that this is not a path to tread lightly. The economic sacrifices required just to go through training are major for someone who has a mortgage and family commitments, and the consequences post-training if a job doesn't turn up need to be considered very carefully.
Most importantly, make sure your partner fully understands these consequences and is prepared to give you her or his full support, because without it you don't stand a chance.
Scroggs