2000 Ford F-250 2 wheel drive vs. 4 wheel drive

I am going to buy a used Ford F-250 and I have the choice between a 2 wheel drive and a 4 wheel drive.
I have never owned a 4 wheel drive and would like to know the costs and benefits of the truck. Is the 2 wheel drive more reliable and cheaper to maintain/repair? I would only be using the four wheel drive when it is needed. I would not need it on a daily basis. Any information on the two types of trucks would be helpful.