I need help with my cockatiel

I recently bought a hand raised cockatiel. I was given food from the breeder but need to buy more soon but can't afford the breeders. Is it possible to switch his food without him getting sick, and how would I do this?

Yes you can switch foods but the problem is if he's used to the one food type, he may reject the new one. But try it anyone.
   
Another option is to feed healthy human food (which is better for him) Cocketiels are seed, grain, sprout, leafy green veg eaters.
   
Here's a list of food that is recommended for tiels & some basic care info for them:
   
http://eclectusparrots.net/cockatiels.html

you should be upchanging the diet anyway to fresh like apples without the seeds, tomatoes, ect, and yes you can change the food its not a problem, prices vary from store to store. Go shopping