How can you validate a business idea, while in stealth-mode?

I'm in very early stages of pursuing a business idea I really like. Usually I think being stealthy is a bad idea, but since the development stage will take a very long time I prefer to stay quiet, until I can get a working MVP shipped. I interviewed some friends who are in the target crowd, and they seem to love the idea as well, but this doesn't count as real validation. Obviously, I don't want to spend many months of development on a product that no one will use. So real validation is needed. But how can I validate the business without exposing everything so early on?

Customer Development is key to validating an idea - find prospective customers who are willing to give you ongoing feedback on your product as you build it and to answer your questions about how they would use the product. Customers loving an idea is NOT validation, you need a confirmation that 1) the problem you are trying to solve exists 2) your product solves that problem. Ideally, have at least 1 customer try to use your early version and stop adding features when they tell you the product already solves some problem for them.

I would strongly recommend to read Steve Blank's blog and book Entrepreneur's Guide to Customer Development. You would probably want to implement a "Concierge MVP".

Also, do extensive research to confirm the problem you are trying to solve has not already been solved. It's not uncommon for startup founders to discover competition after launch or while building the product. 1st page results on Google isn't enough as you need to know what phrases to search for and your competition might be describing the solution different from you. Again, talk to prospective customers and ask them how they solve the problem now.

I also agree with Nick that you are likely overthinking what your MVP needs to be and there is potential for simplifying. If you are not scratching an itch, your customers should tell you what the MVP needs to be.

The need for stealth mode really exists in very very few cases - usually those where first mover advantage appears to be critical to success.

If you believe the development stage, of the MVP, will take a long time, then you're probably not building an *M*VP. Break the development into smaller chunks.

If you really cannot break down, or speed up the development, then you must continue to do validation (actually, you should continue to do this anyway) - but you shouldn't be focussing on validating your business. You should be validating the problem and customer situation. Your product/business will be a consequence of what you have learned.

Obviously, at some point, you'll stop learning and have to start ensuring that people will use/buy your product - at that point you're either going to break stealth mode, or, be so confident, that you can keep moving forwards regardless.

A not to inexpensive way for stealth startups to validate is to go directly to your target audience on an individual basis.

Offline.

That means you won't be able to use Google Adwords, etc to speed up this process (or do it in a cost effective manner).