if it's a 2 story, you will want the master downstairs, even if it's not your "last" home, if one of you has surgery, or if one of your parents need to stay with you for a time, you'll be glad of this.
a great/or not, depending on how you look at things, place for ideas, is pintrest, look at the category for home, or dream home, something like that.
another thought.....think about what you want for your backyard area, do you want something that will require cement poured? can you get that planned and approved now? can you get that poured by the builder? it will may be a whole lot easier to do now, and cheaper. you wouldn't have to finish it off, but anything that requires cement typically has to go through the city and the HOA, after the initial build.