It's not too late, but make no mistake, it's a long hard expensive road ahead, with no guarantees. And in the early days, the pay is crap. I'm not sure what your personal circumstances are eg married with kids and mortgage or single and financially secure, but if it's the former you need a very understanding family, and a partner who is earning a reasonable income, cos seriously you could earn more stacking shelves at the local supermarket than what you'll earn instructing in the 1st couple of years.
That being said, if you have the passion, the drive, and the persistence to get there, I'd say go for it. You don't want to be looking back in 20yrs regretting not giving it a go.