Hmmm, all of this depends on how much you are wanting to spend on the property itself. I mean, 20% of $500,000 will make a different payment than 20% of $100,000. And, from what's left is how your mortgage is determined. On that amount, the interest is calculated.
It sounds like it's time for you to have a meeting with a loan officer that you trust in order to get answers to all of your questions. Please let me know if I may recommend some mortgage people for you to contact. I have some wonderful folks who would take very good care of you.