I will start by saying that I have zero first hand experience of this approach and zero mechanical knowledge but, like many millions of people, I have watched with interest a number of these rebuilds on YouTube. The most notable of course being Mat Armstrong, an East Midlands based mechanic, who has amassed 6.3m subscribers worldwide by buying crashed cars (mostly from Coparts) and rebuilding them. He only buys luxury and sports cars, but the principles are the same. If I was to sum up what I have learned from watching quite a few of these rebuilds, it is the following; 1) The damage that needs repairing is never restricted to just what you can see from photos, or even an on site inspection. Every rebuild has uncovered multiple, and often difficult (and expensive) to fix issues. This can often involve welding structural elements or having to source difficult to obtain parts. 2) The time that it takes to complete these rebuilds means that it would almost only ever be viable if you can do the vast majority of the work yourself (as @kezo has done). If you had to pay someone commercial rates to undertake the work I can’t see the sense in it. It’s also worth keeping in mind that due to the size of Mat Armstrong’s following, and his savvy use of YouTube as an income stream (he makes his money from YouTube, not the cars), he won’t pay anything like the rates that a normal punter would pay for using third parties (bodywork, paintwork, electrics etc) due to the publicity that these companies generate from his vast following (I suspect that much work is done free of charge as a result). 3) Mat Armstrong keeps most of the cars that he rebuilds, or ‘gives them away’ through raffles at £10 a ticket (raffles that generate an income per car of many times what they are worth), so you never really hear about resale value post rebuild. However, any car that has been written off or crash damaged, even when rebuilt, is never going to be worth the same as a car that hasn’t. I’m sure that there are some great success stories out there from people who have managed to buy their dream car for a fraction of the price and, even after the cost of the rebuild, have still saved a chunk of money, but I strongly suspect that just as many people have had their fingers seriously burned by completely underestimating the level of damage. After all, cars are written off for a reason! In summary, I would only go down this route if I could do the work myself and did it as a hobby, not expecting to make any money from it then, if you do end up making money, it’s a bonus.
Salvage Rebuilds UK is another such site however, they have the equipment, which is out of reach of your average backyard mechanic, who’d be a fool to tackle anything with structual damage and whilst these guys are more fun to watch than the BBC, they are the wrong people if your in the market wanting to have a go yourself as a beginner. Cars for Paul (ex mechanic) and beginners on their first or have done a few cars are by far the best to gain knowledge on the type of vehicles to tackle.
Were lucky, my son was head tech at Audi, went through evey department at Bentley and is now has is own business situated next to body repair shop owned by a friend he grew with and of course little old ElectroMechanical myself😂 with cat U,X and repossessions when we have time.