This is something a lot of people ask me when I tell them that I am building an aircraft. Their thinking is, you'd have to be a multi-millionaire to be able to undertake such a project. Then there are some that would try to tell you that you can really do it on a shoestring budget. The truth, as always, is somewhere in between. You certainly don't need to be a multi-millionaire (though it would help) but it certainly would help to have some disposable income. Now, 'disposable' really is a key word here. It's actually not the amount that is really important. It is the fact that the money you are putting in the airplane project comes with no string or baggage attached. Don't think of it as an investment. Don't think you will save money on travels in future. And don't even think about financially justifying what you spend on the project to anyone including yourself. It is money that is 'disposed of', as in gone.
Now, when you are trying to figure out a budget for an aircraft project, what you need to remember is that you are making trade off between money and time. In general, the more money you spend, the quicker the project will be in the air. Already flying homebuilt are often traded at prices that rivals the factory-builts. Plans and instructions, on the other hands can be obtained for a few hundred dollars. In the case of the latter, it is not uncommon to see a project that are hand built over a few decades. Modern fast build kit saves a lot of time, but then often cost tens of thousands of dollars.
In case of a Velocity, the most basic kit can be purchased for a little over $20,000(US). Since this price does not include the engine, propeller, instruments, or radios, you will need to factor in those. Using used engines, instruments and basic radios, it is quite possible to put one together for about $40,000(US). In other words, as much as it would cost to get a luxury car. Of course, you will not pay this sum all at once. Once the kit is paid for, you can get component you need piecemeal so that you don't get hit by a huge up-front expenditure.
Now, that's the baseline. Want to fly quicker? Spend some $$ for fast build kit. Want IFR panel? More $$. Don't trust those used engine with questionable history? More $$. Want state of the arts EFIS and autopilot? $$$$$! You get the picture. You'll quickly notice that the project can really start to drain your pocketbook.
Like everything else in aviation, it's all about compromise. It helps to be able to differentiate from "wants" from "needs". It helps to be able to stack rank all the different options. In the end, it comes down to this. How much can you 'throw away' for your dream? The project will cost you at least that much and most likely, more.