I work as much overtime as I can (firefighter), and have a second job as a sailing coach. I have a second bank account for plane funds, and fill it only with that extra money. Last year I used a 0% intro rate card for some large purchases, but made sure to pay it off in the next few months before buying anything else. It helps that I have no kids, but am getting married in 2015 and would like to be done before kids ARE in the picture. Fortunately, she approves of the project and likes to fly.
My goal has been to not go into debt for the project or dip into my normal savings, and so far so good. I still need an engine, and am deciding how to handle that. Will probably go used, mid-time. I will probably sell my boat and use that money, but since I use the boat for work, I may keep it as long as I am making money and get a small loan instead.
Lifestyle-wise, I drive a 13 year old, paid-off vehicle, don't go out partying much, and buy new clothes only when the wife-to-be makes me. For the most part, if I'm not working, I'm building. I am keeping the plane simple, and probably won't paint it any time soon. Basic glass panel, because these days it's just as cheap and more reliable (IMO). I scour the VAF classifieds for deals and have bought a lot of equipment at great prices on here, saving thousands.
It's doable on a budget, but helps to not be in a hurry. If you're out of money for a while, there's usually still something productive you can plan or work on until you can afford the next piece. Keep it simple and look for good deals.
Chris