LS is pretty big, so it depends on where you live as to which way into the city is faster. If you in the northern parts of the city it's quicker to to take 470 to 70. If you live the south parts, it's quicker to take 470 to 71.
I can't help you too much on specific townhouses or duplexes though. LS does seem to have quite a few nice duplex/townhouse areas though. I would look around 470 and Lakewood and out south around Raintree. I think there are a lot out near the Todd George exit as well.
If you have the money, I would try to get into Arborwalk or New Longview. Both are large new urbanism developments that are very walkable and are based off old style neighborhoods like Brookside. I'm not sure if they have a lot of rentals though, but there is always condo type places for rent in developments like that.
Arbor Walk Lees Summit New Homes Villas Townhomes | Lees Summit Office and Retail Space by Gale Communities
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