If your are placing an offer on a home from an individual seller (not a REO/Bank Owned) then the Earnest money is negotiable.
Right now we are seeing many multiple offer situations. If you wanted to make your offer look even better, you could raise the amount of earnest money and that could make your offer stand out over another offer.
I would be happy to answer any more questions you might have.
The right amount of earnest money is whatever you think means you are serious about buying the property. Typically people will expect approximately 1%, but I have done significantly less than that and had deals close.
In some cases though the seller will have a required amount they want you to put up for a property. Now keep in mind you need to know the terms of the agreement. In most cases earnest money is refundable but when you are dealing with either builders and banks they sometimes find ways to keep your money if you do not close the deal.
When you are dealing with a builder, then they will usually have a set amount. However, it can vary if you are adding things at the design center. I'm guessing that you are working with Elmer Carino if you are building a Landon home in Little Elm? I would advise of obtaining a Realtor to help you through this process. I will help you if needed. My contact info is below.
If you are buying a repo home then No it is not negotiable, there is a $500 or $1000 earnest money required. Homes that are owned by a person can be negotiable. Earnest money shows how serious you are as a buyer! So the more you put in too earnest money can put you 1st in line :)