If you want a private business lisence you must pass a basic firearms safety and marksmanship course. If you want a home mortgage, you must pass a basic firearms safety and marksmanship course.
What are the downsides to this?

How's this for starters......

There are people who are perfectly good citizens who lack the physical capabilities to pass these courses.

Because of a physical disability someone would be incapable of getting a mortgage or owning a business?

Funny, I think Stephen Hawking would be an asset to ANY community, regardless of whether he can pass a basic marksmanship or firearm safety course.