I wonder how many unfinished projects sit in garages because someone underestimated the difficulty and cost. Not to diminish someone’s enthusiasm, but building a car from scratch can be daunting. My first advise would be to define what you want or like, settling for less means your not in love with it. Next is start with a good complete candidate. Getting bogged down in rust and body repair is costly and frustrating. Then figure out what you are capable of and where it might be better to get help. After all very few do it all by themselves. As far as age and experience as a factor, no doubt hopefully one acquires knowledge and skills over time, it is never too late to learn. My suggestion would be buy a good running example, drive it for a while to see what it needs to be what you desire and don’t destroy it into a pile of parts accented with uninstalled shiny aftermarket pieces in boxes for sale. That would be the Pandora’s box of unfulfilled dreams and realities.