Mr Angry There is a world of difference between a player being encouraged to consider a new career post-retirement, and someone who has a full time job and plays professional football as their 2nd job.
Also, if you look at your employment contract there is almost certainly a clause in it preventing you from having any other employment; no reason a footballer will be any different.
As for Insurance, their are certainly clauses in players contracts that prevent them - for example - playing other specific sports due to the insurance on them being null and void if they get injured whilst doing something proscribed (which is why so many players are golfers), and I would imagine there are likely to be similar clauses preventing players from having full time outside employment.
Back in the day, I remember that Martin Peters owned a couple of Insurance Brokers in (iirc) Essex, but whilst he was playing he wasn't allowed to work at his own Companies; it was only when he retired that he went full time into the industry.
You can’t be serious that employment contacts forbid you having other jobs ! They might forbid you working in competing areas but huge numbers of people in this country work in more than one job out of economic necessity ! Sorry, that kind of shows you must be totally out of touch with the world of employment.
Insurance exclusions obviously prevent footballers doing things with high risk of injury but they wouldn’t exclude running a soccer school, or being a personal tutor or a mortgage broker….
And plenty of other sports have players doing stuff outside their sport. England rugby currently have a player doing a medical degree which involves working in hospitals, some Welsh and All Blacks players have family farms they work on did Alistair Cook.
I agree combining football and another career may not be easy but there is no reason why it can’t be done - certainly there is no FA / FIFA rule stopping it.