Pre-qualification is a free service. Most home sellers will consider you a serious buyer if you have been pre-qualified.  Pre-qualification eliminates a major contingency for the seller.  Pre-qualification means that, if everything you submitted to your loan officer is true, you can buy a home up to the limit of your pre-qualification. Getting Pre-approved is even stronger. Pre-approval means that you are guaranteed a loan up to "x" amount if the house appraises. You benefit by being able to acquire the home of your choice.
Put yourself in the sellers' shoes. Two buyers are interested in buying your property. One has a piece of paper that says he/she is qualified to buy your property. The other is offering a slightly higher price ($1,000 to $5,000), but the offer is predicated on obtaining loan approval. Once a seller enters into a "Purchase and Sales Agreement" the property cannot be sold to another party as long as the conditions of the contract are met. If the sale is not completed because the buyer could not get  loan approval, the seller has lost valuable time and the house has to be marketed again. In the meantime, other, qualified buyers may have been lost. A Buyer's Agent will point out the length of time the house has been on the market and every buyers will wonder why nobody else wanted the home. Typically the price received for a property declines in direct proportion to the length of time it stays on the market.
The average price of homes has escalated to a level where a few thousand dollars is seldom the reason one offer is accepted over another. Most sellers are motivated by a desire to return to a normal life.  The strongest buyer usually gets the house.
Any Realtor listed on this site can provide you with the names of two or three lenders who will gladly pre-qualify you. You are not required to use a local lender, but it is to your advantage to use someone who knows the area. The title company or closing attorney must work closely with the lender who must contract the services of a local appraiser. Every closing has some last minute emergency due to an oversight. When all parties are local problems are much easier to resolve insuring a smooth and timely closing.