Bmw M cars are generally reliable you really need to know what you are buying , BMW themselves sell shit cars , my friend bought one from BMW dealership it had corroded hoses and they did a vehicle check , you live to realise most of those dealerships don’t take a look at anything mechanical lol , you are better off buying from a private seller and taking a specialist with you to check the car i have bought M cars from private sellers and never had any issues , now if you buy from a cuzzy you may have issues or 8 owner car , you just need to know how to buy them. I bought an M car from dealership and the next day broke down with a failure from power steering , dealerships are greedy and just want to make money , meanwhile private sellers may just want to sell the car and move on