I wonder how many of the people telling you not to build have actually done it.
I have,
Great experience. Most of the current Sportplanes run out about $100K plus. My plane cost me $55KCdn (about $45K US at the time) took 1 year (800 hrs of work) and was not a fast build kit. Choice of construction method and style is growing all the time.
You need to work out a few things first,
1.) Mission. What do you want to do with it and will it satisfy the mission requirements?
2.) Building method. Frame, Steel, Al, Fabric, F/Glass etc? Which are you comfortable with?
3.) Experience of other builders, number finished, number failed gives a decent indication of time and difficulty.
4.) A good internet group with a tips file, guys often on line and knowledgeable help is VITAL in this day and age. I would not even contemplate building a plane that did not have 80 to 100 or more Inet participants in the group.
5.) There are times it gets tedious or you run out of steam. Are you stubborn enough to see it through?
6.) Money. My kit was $22K, the engine was $11K My final bill was $55. The rest was shipping, tax, instruments ( about $5K!) , paint (about $1500) booth rental ($600) and lots of little odds and sods, oh, and inspections and legals ($2,000 plus!)
BUT, I loved it, and when I have built the garage on this house I expect to build another plane, ( but I have to tell my wife first, that is almost a bigger hurdle than building the garage!)