All three sentences are about an expected future event. Unfortunately, despite his writing skills, Ronald Sole's answer is wrong. "Have waited" is past tense. Putting "will" in front of "have waited" puts it in the future. I will explain sentence by sentence.
The first sentence makes sense and is possible in the following scenario.
If you were to say
"I realized that, in order to make a real difference, I would need a
that would either mean you already have one and you're telling a story. You should probably say
"I realize that, in order to make a real difference, I need a MBA"
if you're talking to someone about why you want the MBA. It kind of depends on what you're ...