Getting an older dog is an excellent idea... no annoying puppy stage with teething and toileting issues! :-)
And best of all, you're giving a dog a second chance at a great life.
My only advice is to give the dog time to settle in, and be realistic about what you expect at the start. We see a lot of people here who take on a dog and expect it to instantly fit in and "gel" with everyone, and that's not particularly fair.
Wait, I've got one more bit of advice, research the breeds you're interested in, even when getting a mixed breed there is often a "dominant" gene, so find out what traits are common.
Good luck :-)