Generally SaltyNever, EVER, buy someone else's unfinished project car, esp. one with such high mileage. This thing is a black hole waiting to suck your wallet dry which is certainly why the seller is trying to unload it.
I have this same model and year but it is unmolested with very low mileage. I've been tempted by various 3rd-party mods in the past but decided that 350+hp with the official BMW upgrades is quite enough. Squeezing 6–700+hp out of the N55 engine is possible with enough money thrown at it, but not for very long before things go kablooie.
https://carsandbids.com/auctions/9AEWp0Wo/2014-bmw-335i-sedan
