As ever, don't build it if you can buy it. Many years ago when I was into cars I fancied building a hot Mini. So I had a look at what was out there, priced the bits, and fairly rapidly arrived at a figure of £5k. At that time you could buy a very nice Peugeot 205 GTi for that sum, and have a ready-made car that would run rings round any Mini. If you want to build it because you want to build it, then crack on, but don't expect to ever see the money again. Rather like the kitchens and bathrooms thread elsewhere, if you buy a house in decent order for £200k and spend £50k on a new kitchen, bathroom, windows, whatever, you don't have a house that is now worth £250k. Do it for yourself at the time if you want to, but if you can buy what you want, then do it.