What happens if you attempt to contact or do business with a covert/secret agent front?

I think most of the restaurants with no customers and aquarium shops with no fish are fronts of a different kind, namely money laundering for things like drug dealing. The business will claim big profits and that lets them get the cash into the system, when in reality the business doesn’t do a real sale in a year.

I imagine the better and smarter ones do try to at least appear plausible, but they get lazy or stupid and you have well obvious fronts.

Wow. I just realized that I’ve dealt with at least a half-dozen CIA fronts during my life.

I suspect it won’t exactly be beyond the CIA’s budget and connection to get at least a well stocked shop and or at least engage in some legitimate business ventures. You can hire a small staff to take care of that end and everyone else can concentrate on what is necessary.