How to know a niche is worth the time?

[tathagata]

There is no general rule you know. Basically experienced marketers just assume in their instincts and also its a fact that experienced marketers don't just invest in an untested niche.

Here is a quick thing that you can do if the niche its too small. Invest some money in ad campaigns and check how its goes. If brings the capital price with some profit then spend more money and time, otherwise not.

How much budget should I invest on?