ROI aside-
35 isn't too late. Saw plenty of pod students and residents who were that age. Some (not a majority) were older.
Consider the other side of things.
Married?
Kids?
Do you understand what podiatry school will expect from you in terms of studying hours and rotations?
Board exam dedicated studying time prep?
Financially you will not be holding a job or providing any significant income for 4 years?
Then you go to residency-
If married with kids, does your spouse realize they will be a single parent for a majority of the time?
That your salary will be close to what you are making right now or a little more while you work 14+ hour days?
Do your kids realize you will not be there for their school stuff, sports stuff, just around in general?
Then look at yourself and current health-
Do you have the mental discipline to study for hours at a time?
Do you have all your emotional baggage sorted out?
Will your body at 35 be able to handle call schedules, driving in the dead of the night, being in the OR, seeing consults while running on 2-3 hrs of sleep?
Forget the ROI stuff for a second and think about the above.
If you're still game then apply.
Looking back if I was 35, I wouldn't do it.
I wouldn't do it in my late 20s either.
Hindsight.