It is not required to present an offer, but is highly recommended.  Especially in a Sellers market, where often times there are multiple offers in play.  Not uncommon for two offers to be identical in price, but one buyer is pre approved and the other is not.  Guess which one wins out?  There are occasions where it may make sense to secure a property without the pre approval in hand, but as a general rule of thumb, you want to be pre approved.  Don't you wish to know how much a loan is going to cost before you go forward??  We have mortgage brokers we have worked with and trust should you need recommendations.