Food and vet bills are going to be your biggest.

Other things to keep in mind..

monthly heartworm/flea medication
grooming (optional for a lab if you want to give it a bath yourself, or if you don't mind doggy smell)
The cheap foods are not worth it.. you'll have a healthier dog (and less vet bills) if you get quality food such as Nutro, Royal Canin, Bil Jac etc.
Also your bills are going to be higher for a dog as big as a lab. You may want to consider a smaller breed. I'm a dog groomer so I have first hand experience with hundreds of breeds.. if you have any questions I can likely help!