The key factor will be how cold it gets during wintertime in your area. What city are you in?
Yes, a lemon tree can be planted from a seed - and you can even find seeds in lemons that have already begun to sprout...but better would be to buy a small lemon tree and plant it - if your area will support one.
They do not handle frost well at all...so if your area actually freezes, then you'll have no luck with one outdoors.