That's sort of a trick question... I have worked various MLM's and biz opps since 1994 or so and through the years I've talked to MANY MANY people about this subject in one way or another.
I discovered early on that people's "tolerance" for risk and pain was WIDELY varied...
Some would spend every last cent they had to place some ads or further their knowledge to get ahead and some wouldn't toss a penny into a wishing well even if it was guaranteed to pay out like a loose slot machine.
In regards to how long to stay with a business opportunity that you are not making money with
Here's what my years of experience showed me..
Some people will work an offer for just 4 days then all of the sudden bail like their ship was going down once they've sniffed out the "next" HOT offer. Some will work a business for years even without doing much better than breaking even.
Quick Note: Those "4 day bailers" usually never work ANY program they find... they are so busy scouting the "next" money making program that they never work the one they're in.
They seem to think the offer(s) will just start paying them money without doing anything.
It really depends on you... If I were talking to a lead on the phone or by chat let's say and they asked me this question about the business opportunity I was pitching, I'd say, "Well that depends on how you're going to advertise or promote this offer"... "If you give it a hobbies effort you'll get a hobbies result".
I'd also say, "If you're not going to put money into this and place ads or try and duplicate my efforts you're better off not even joining".
This is a "safety" question.... a "develop an exit strategy BEFORE I really start to advertise" question... these questions never imply that a person plans to stay long term.
It's like a person that wants to buy XYZ product, but asks the seller what their refund policy is...
I don't think there is any "standard" answer one can give here... only the individual can determine that answer.
No business is successful without time in the trenches
If you're spending money without generating leads then question WHY then learn how to correct that.
If you're building a list and gaining subscribers, but you get no feedback, make no sales when doing a broadcast or people are unsubscribing left and right question WHY then learn to correct that.
If your solo ads don't produce fruit ask WHY then learn to write better ads... learn how...learn what makes people buy.
NO business will dump cash in your closet on autopilot without time and effort put in.. the ones they say they will run fast the other direction.
Telling someone a time frame to bolt on a business is impossible, because we don't know the work ethic of that person.
This is MY 3.5 cents on this matter hope it helped you