It doesnt matter if they have issues.

You're buying an approved used BMW so you'll get at least a 1 year warranty. Try and negotiate 2 years. Most dealers up here will give 2 years.

Just mind that only take the service pack if you intend on keeping the car long enough to get the value out of it. It usually covers 1 oil services, set of spark plugs, 2 air filters and a pollen filter and brake fluid change. Be mindful that BMW only require 18k mile oil change intervals now.

http://www.bmw.co.uk/en_GB/topics/owners/service-and-maintenance/servicingoptions.html