I say you should use only one, especially if you don't have enough money for two. Just wash them thoroughly after every use so your makeup doesn't mix!
Your friends could be backup or maybe you could teach them how to play a cool instrument like guitar, drums, etc. Just because they might not be able to write...
It should still work. It is better to use a wet beauty blender for foundation and cream contour -- just make sure that your beauty blender is not soaking wet,...