In my experience (which i'll summarize that at the bottom), I think you need a few things to build an airplane:
1. Space. I assume you've considered that you'll need at least a one-car garage worth of space to build the components, and then something two-car sized or a hangar to assemble in. I started in a basement room in my townhouse that was the size of a one-car garage, after working out that I could get the tail surfaces and wings out when the time came. Fuselage was another issue that I planned to deal with later.
2. Time. You need to be able to dedicate at least an hour a day to keep the project going. If you miss even a day, it gets harder to come back to it. If you plan to work on it full time one day a week, you'll take longer, as you'll spend half the time remembering where you left off last week. Shorter bursts more regularly are better.
3. Support. You need this to make the Time. If you're single, it's easier. If you're married or living with someone, you need their support and sometimes their boot in your butt to get in to the workshop for an hour a day. Eventually you'll need their help too, as you start bucking rivets in awkward places.
4. Money. The kit price is known, and you can figure out with a few google searches what it's going to cost to put together a stack of instruments, an engine, an upholstery, and paint. Once you've done that, and made a guess how long it will take you to build, you can work out a budget for how much it will cost you as you go. Once you've done that, don't give up.

Money always seems to be available once you've decided you can do this. Really, if you're going to biy a plane instead, you'll need the same money. All that changes is when you start flying.
Now, i'd like to say that i'd completed an RV and could say that I speak from experience as a result. But I can't. I started 10 years ago at 28, and i've still only got the tail kit, and it's only partially completed. Just this month I purchased a completed RV-6 because my desire to be up flying has finally outweighed my desire and patience to be down here building. That, and at the rate i'm going I figure by the time I finish i'll need Depends rated for +6/-3G before i'll be able to enjoy it. One of the goals when I started was to have the RV flying before I was 40, and I can see that there's no way i'll finish the -7 by that time.
In my case, I lost a lot of Time due to changes in employment (both expected and unexpected) and change in residence (townhouse to house). And while I love my wife of 20 years dearly she isn't really an aviation person and as a result it probably wasn't fair to expect her to Support my need for the Time to work on the project... Especially when we also needed to renovate first the townhouse, and now our house. Space has never been an issue, the townhouse was good for the first half of the kit, and the house now has a two-car garage that would let me finish it. Money hasn't been an issue either, after all I did just buy a completed -6. The money always seems to be there when you need it.
For now the -7 will remain a side project, or maybe it'll be a retirement project. Although by then there may be an RV-17 instead. One option is to finish the tail and put it on the -6, it seems a lot of people are doing that now. But i'll fly the -6 for a while first, and decide what i'd want to do differently before I go back to building.
For you, 24 is a good age to start. But get going on it, and get it done quickly. The main reason is that if you don't, you'll fall behind all the other projects around you, and get lost in the desire to be up there flying rather than down on the ground building. You'll also fall victim to encroachmnets on the other requirements... You'll find a girlfriend and then a wife, take on more important roles at work which take more time, and eventually you'll buy a house that takes more money. Each of these are double-edged swords that have the potential to help or hinder your progress. Choose wisely!
So good luck, and get going!