New Jersey BMW CCA

I’m beginning to look for a solid preowned e90/92 or 1 series 6 speed manual as an extra vehicle. While I’d like the extra power of the turbo over the 230hp or 255 hp N52/N51 I’m more concerned about reliability and cost if I keep it past 150k miles. Can anybody share any facts on the difference in long term cost of the turbo six and associated hardware over the normally aspirated motor?

Thanks very much, Bill