and how profitable you think?

and how you can learn to build them? do the kits come with instructions?

how much do you think people would pay you to build them for them? and where you could find customers at?

btw, is this popular in Britain?

You cannot build antique cars as they would then be newly built cars. You can restore antique or old cars back to what they were though but this is very specialised and parts often have to be made specially by the restorer.