I'm about 3 months down this path. Here's my approach and advice...

----My Approach----

I'm a technical founder with no co-founder. 12 years of back-end development experience. I think I am pretty good on the sales and marketing side (although it's still unproven).

I enrolled in a local business mentorship to keep me sane (and get me out of my home office every once in a while), get feedback from other entrepreneurs and get help with various parts of starting a business.

My general life philosophy is to jump in, then figure out how to swim.

I'm using a combination of savings and friends & family to fund the project. I currently have 6 months of runway to get ramen profitable.

My product is B2B SaaS. I need about 20 customers to get ramen profitable.

I am outsourcing the design, which is my weakness. Everything else falls on me.

It took 3 months of 8 hours a day, 6 days a week to get the beta version built. Demos are actually going out tonight and public launch is next week...yikes!!

I feel very confident that I can sell 20 subscriptions in a few months, with only half my time dedicated to sales.

----My Advice----

If you're not building a B2B SaaS product, don't quit the day job.

If you are building anything consumer-focused, definitely don't quit your day job.

Do you work well under pressure? I have a wife and a son and a decent monthly nut I have to cover. I work best under pressure. But I have never felt this level of sustained pressure before. It's incredibly difficult to keep pushing hard all night every night (I work at night when the house is quiet). If you don't thrive under pressure, don't quit your day job. Be brutally honest about this one because it will crush you if you think you are but aren't.

Outsource your weaknesses. It usually takes a while to find any technical support that's worth a damn. Be prepared to pay top dollar for it. Post your needs on all the outsourcing/freelance/crowdsourcing sites. Post it on craigslist (both locally and elsewhere). I found that each site has a specific pool of talent that's worth a damn. This will take longer than you think. You'll have to cycle through several 'perfect matches' before you find somebody that's the right fit. This piece really comes down to serendipity and luck and there's not much you can do to hack it (other than being persistent and patient).

Estimate how long it will take to build the MVP. Be conservative. Then double it. Seriously, double it. Then you'll be in the ballpark.

Spend half your time on non-coding stuff. This is the hardest part for a technical person, but vital. Even if you have a bizdev co-founder, it's your idea, your vision and you're the only person that will ever understand it.

Again, assuming B2B, get out a talk with customers ASAP. Talk with 3 potential customers. Pitch each one, refine the pitch, go to the next. This is absolutely paramount. Everybody says to do this. DO NOT UNDERESTIMATE THIS!!!

I was unable to find a co-founder. I think this is a blessing in disguise. I tried to recruit one at the start (spent 2 months on it). We couldn't agree on terms. That 2 months was not very productive. We'd spend a lot of time talking, not much time doing. It's incredibly easy to just spend hours talking, theorizing, hypothesizing, thinking. None of that really matters. The only thing that matters is shipping a product. Even if it's complete garbage, ship the damn product ASAP! If you engage potential customers (see the previous point), you'll have a significantly better chance of the product gaining some initial traction.

Last piece of advice would be: you have to sell this product. You can't hire anybody else (even if you have a biz dev co-founder who should also be selling) to do this for you. If you don't have the nerve to get in front of a customer, the skill to communicate with them effectively, the thick skin to hear how much your product sucks and the balls to ask them for money anyway, then don't quit your day job. If you are the idea person, then you HAVE TO SELL IT!

---End Brain Dump---

Hopefully there's at least one or two nuggets of truth in there that resonate with you.

Keep us posted on your progress. Everybody on HN is here to help you. Just ask.