mortgage pre-approval letter hunting

[OhioGuy]

My wife and I have noticed that there are more and more bank owned
properties coming on the market. Interest rates have also recently
dropped back to what they were in 2003 as well.

We are interested in getting a 30 year mortgage this time around,
though we will likely pay it off a lot sooner than that. I think we
need a pre-approval letter to make sure we can make an offer quickly
that will be taken seriously.

Anyone have any pointers for shopping around for a good deal on
interest rate?

specs that should affect the loan:

1) we have no debt at all

2) credit rating of 790

3) equity of about $55K in a fully paid off duplex. One side should
bring in $450 a month rent as soon as we move
out, while the other side should bring in about $400 a month
starting in about a year. Each side has 3 bedrooms and 1,300 square
feet of living area total.

4) 30 year term

Thanks!