二周前签了一个买房合同，下个月办手续。今天有空打了几个电话， 了解一些贷款
的事情。

There are big difference about the closing costs. The main difference is
lender fee and interest rate. The big banks charge more lender fee with
a higher interest rate. The cheapest lenders are from the internet.

I searched: bankrate.com and yahoo-finance for fixed 15 year loan. The interest
rates vary from 2.875 to 3.25%. The lender fees vary from paying $1,995
to -$1,600.

For example, I could get a rate of 2.875% without paying lender fee, or
get  a rate of  3% with a bonus of $1600.  Majority of banks charge 3% rate, but
you have to pay $500-2000 lender fees.

My suggestion is: search online first, then to call at least 3 lenders to
get a better rate.

Good luck!