Ideally if you qualify by the time you are 30 you will be fine! But the earlier the better, or when you reach a point you can comfortably afford the course. If you have to wait longer, not the end of the world and I can testify to that. I just finished 5 months ago at age 34 and am about to start in my shiney new Airbus for BA.
A career to fall back on is a sound investment as well as being able to save some funds. Too many people take out huge loans and spend the first 10 years of their career paying it back.
I would also strongly advise you take some flying lessons in the interim period (assuming you have not done so already). This will confirm you really want to do it and also give you an idea of your aptitude for flying which is also important given you are going to make such a large investment in yourself.
And save, save, save as much and as quickly as you can.
Good luck and hope it works out