About buying.
1. Match the plane's abilities to your expectations. Build a sensible plane first time round.
2. If there is even the tingiest smidgeon of doubt about financial securtiy of manufacturer buy the whole plane except engine and instruments in one hit. Have them crate it on the loading dock before you forward the main payment.
3. Buy the instruments last. Some of the manufacturers cheat on the warranty and do it from date of sale. You don't want them out of warranty before you even test them!
4. If you are a 'wannafly' rather than a 'wannabuild' get the most built kit you can. (EG you can buy an RV with wings built and tanks installed and tested for anly about 3500 US extra. Almost Nothing in GBP!
5. Almost nothing in aviation is cheap. Some kits work out expensive when all is done but those who say a kit is NEVER a cheaper way into a plane are just plain wrong.
6. Join the Inet group for your plane. (I would not build a plane without a group's support.)
7. Allow approx double manufacturer's quoted hours to completion.
8. Budget 10 to 15% for over runs, then work hard at containing cost early on. Remember you will be making important purchases, instruments and avionics near the sharp end of your budget.
About building.
1. While you are waiting build a nice rolling toolchest/parts storage/catalogue system etc. Will Save hundreds of hours.
2. Work within seconds of your armchair. Far too easy to put off a 20 min drive as 'not worth it.'
3. When friends say, "Oh just ask if you need help" ENGAGE THEM ALL. Give them regular times, Learn to work and direct but also make it social too. It is awful being half way through in the hard slog bit and not having help or social contact and lots of them really would like to help. (I was told by several afterwards that they were really upset I did not call them.)
5. Get the manual while you are waiting and work out every possible move.
6. Build every day. A two day 'rest' quickly becomes a couple of months with nothing done.
I think it is a bit like having babies or building a house. The day you finish you'll never do it again. Six months later you can't wait to start the next one.
Been there, done it, love it.