I think it depends on whether the biz has been validated in some way or not. I think the first version of most products should be simple enough to not need 100%

I think it depends on whether the biz has been validated in some way or not. I think the first version of most products should be simple enough to not need 100% dedication in order to build it. If it requires that much focus, you might try shedding some features so that you can ship something while reliably making an income. I WOULD NOT quit my job to build something which hasn't been validated in some way. I have done that and it was a huge mistake. Imagine the following: 1.) you have a product idea 2.) you have talked to potential clients and find out they need it and are willing to pay for 3.) a percentage of them will agree to pay you, specifically you, when it ships 4.) those potential clients know other people in their field who also need your product and are willing to give you a warm intro to them Here we have imagined a circumstance where you have a business with an unprecedentedly high probability of success. Furthermore, it's a circumstance which didn't require you to build or really focus heavily on anything. If you're worried about how long it will take you to get off the ground with something like this, don't. Making the above a reality is so valuable, you can afford to spend a little time on it. After quitting my job and jumping into an idea-phase business, I've raised my standards quite a bit. An idea won't cut it for me anymore. I need validation.