How often can you have to self-induce vomit to start seeing side effects of bulimia?

Not sure.: This undoubtedly varies across people and depends in part on extent of vomiting. It's a bit like asking how many cigarettes are too many. In both cases, the answer is, the sooner you seek help, the more likely you are to get over the problem and avoide later complications. Trying to limit yourself to one self-induced vomiting a week is definitely not the answer.