question on getting tires/rims back to stock

recently purchased my first bmw from a friend of mine, so go easy on me if i forget something or am missing details.

anyway, when i purchased the car it had 20x9 Maas 054 wheels, the ones pictured below. Im assuming to get back to any sort of stock wheel would thereby require me to purchase new tires as well since i doubt that there are bmw wheels fitting that tire size. Basically i want to make that transition as cheap as possible so any input from anyone who knows more about this stuff than me is greatly appreciated.

Also, if its going to be difficult i essential want just more a conservative appearance to the car since big chrome wheels are really "me", so they dont necessarily have to be stock but im not looking to spend a fortune here, im hoping that selling the wheels below on craigslist or whereever would offset the cost of the new ones.

Just try and trade for wheels and tires...