To add to Clay's answer, most banks will only allow you to go up to 45% on your 'back end' debt ratio. There are a few that will allow you to go up to 55%.
There is no 'hit' or adjustment for being a first time home buyer. Rates came up a little today but you should still be to lock in 5.125-5.25% with one point. As David mentioned, rates on a 15 year should always be slightly better.
Every state has different adjustments for interest rates, but overall they are very close. The quotes you see on here are pretty accurate and aggressive.
Did you recieve any incentives from a builder for the purchase? If not, you should be able refinance with no penalty. The reason that your bank says this is that there will probably be a 'recapture fee' that they will have to pay if you refi out of that loan within the first year.Yes, anything that you pay over the minumum payment will go straight to lowering the principal, hence gaining you equity much faster.
It sounds like they used a value estimator to determine your home value. Every major lender has different tools to determine your home's estimated worth. Chances are, that this did not even include your recent addition.
Are you able to make payments above the I/O payment? If so, you can get qualified to refinance at 105% of the appraised value and get into a fixed rate.
Does anyone know of an MI company that will cover a 2nd home in WA at 90% LTV? Borrower has 800 Fico