Correct, but you are referring to an adjustable rate mortgage. I would suggest a fixed rate at this time.
If you can't afford the 20% downpayment, you can put down less and when your equity finally reaches 20%, you can stop paying the PMI (private mortgage insurance) that they make you pay when putting down less than the 20%. I think it's roughly $50-$75/month, I really don't know, I've never paid it.
You should look at the tax savings you'll get with owning a home when comparing rent vs buying. You may pay more for your mortgage but you get some money back at tax time because the mortgage interest is tax deductable as is the Real estate taxes.
The first several year's mortgage payments are mostly interest and very little principle. So mostly all of it will be tax deductible. good luck.
If you wanna throw some numbers up here, we'll help you out.